diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0bdc317..9e02a8c 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -81,13 +81,13 @@ set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
 if(AARE_FETCH_LMFIT)
     #TODO! Should we fetch lmfit from the web or inlcude a tar.gz in the repo?
-    #set(lmfit_patch git apply ${CMAKE_CURRENT_SOURCE_DIR}/patches/lmfit.patch)
+    set(lmfit_patch git apply ${CMAKE_CURRENT_SOURCE_DIR}/patches/lmfit.patch)
     FetchContent_Declare(
         lmfit
         GIT_REPOSITORY https://jugit.fz-juelich.de/mlz/lmfit.git
         GIT_TAG        main
-        #PATCH_COMMAND ${lmfit_patch}
-        #UPDATE_DISCONNECTED 1
+        PATCH_COMMAND ${lmfit_patch}
+        UPDATE_DISCONNECTED 1
         #EXCLUDE_FROM_ALL 1
     )
     #Disable what we don't need from lmfit
@@ -358,7 +358,7 @@ set(SourceFiles
 add_library(aare_core STATIC ${SourceFiles})
 target_include_directories(aare_core PUBLIC 
     "$<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>" 
-    "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>" PRIVATE ${lmfit_SOURCE_DIR}/lib
+    "$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>" 
 )
 
 target_link_libraries(
@@ -369,7 +369,7 @@ target_link_libraries(
     ${STD_FS_LIB} # from helpers.cmake
     PRIVATE 
     aare_compiler_flags 
-    "$<BUILD_INTERFACE:lmfit>"
+    $<BUILD_INTERFACE:lmfit>
 
 )
 
diff --git a/include/aare/ClusterFile.hpp b/include/aare/ClusterFile.hpp
index 289647d..6bd231e 100644
--- a/include/aare/ClusterFile.hpp
+++ b/include/aare/ClusterFile.hpp
@@ -243,8 +243,9 @@ ClusterFile<ClusterType, Enable>::read_clusters(size_t n_clusters, ROI roi) {
             fread(&tmp, sizeof(tmp), 1, fp);
             if (tmp.x >= roi.xmin && tmp.x <= roi.xmax && tmp.y >= roi.ymin &&
                 tmp.y <= roi.ymax) {
-                clusters.push_back(tmp.x, tmp.y,
-                                   reinterpret_cast<std::byte *>(tmp.data));
+                // clusters.push_back(tmp.x, tmp.y,
+                // reinterpret_cast<std::byte *>(tmp.data));
+                clusters.push_back(tmp);
                 nph_read++;
             }
         }
@@ -268,9 +269,10 @@ ClusterFile<ClusterType, Enable>::read_clusters(size_t n_clusters, ROI roi) {
                     fread(&tmp, sizeof(tmp), 1, fp);
                     if (tmp.x >= roi.xmin && tmp.x <= roi.xmax &&
                         tmp.y >= roi.ymin && tmp.y <= roi.ymax) {
-                        clusters.push_back(
-                            tmp.x, tmp.y,
-                            reinterpret_cast<std::byte *>(tmp.data));
+                        // clusters.push_back(
+                        // tmp.x, tmp.y,
+                        // reinterpret_cast<std::byte *>(tmp.data));
+                        clusters.push_back(tmp);
                         nph_read++;
                     }
                 }
diff --git a/include/aare/ClusterFinder.hpp b/include/aare/ClusterFinder.hpp
index 9a15448..6a8fec4 100644
--- a/include/aare/ClusterFinder.hpp
+++ b/include/aare/ClusterFinder.hpp
@@ -140,9 +140,14 @@ class ClusterFinder {
                     }
 
                     // Add the cluster to the output ClusterVector
+                    /*
                     m_clusters.push_back(
                         ix, iy,
                         reinterpret_cast<std::byte *>(cluster_data.data()));
+                    */
+                    m_clusters.push_back(
+                        Cluster<CT, ClusterSizeX, ClusterSizeY>{
+                            ix, iy, cluster_data.data()});
                 }
             }
         }
diff --git a/include/aare/ClusterVector.hpp b/include/aare/ClusterVector.hpp
index 0e47b51..073df13 100644
--- a/include/aare/ClusterVector.hpp
+++ b/include/aare/ClusterVector.hpp
@@ -100,25 +100,22 @@ class ClusterVector<Cluster<T, ClusterSizeX, ClusterSizeY, CoordType>> {
 
     /**
      * @brief Add a cluster to the vector
-     * @param x x-coordinate of the cluster
-     * @param y y-coordinate of the cluster
-     * @param data pointer to the data of the cluster
-     * @warning The data pointer must point to a buffer of size cluster_size_x *
-     * cluster_size_y * sizeof(T)
      */
-    void push_back(CoordType x, CoordType y, const std::byte *data) {
+    void push_back(const ClusterType &cluster) {
         if (m_size == m_capacity) {
             allocate_buffer(m_capacity * 2);
         }
         std::byte *ptr = element_ptr(m_size);
-        *reinterpret_cast<CoordType *>(ptr) = x;
+        *reinterpret_cast<CoordType *>(ptr) = cluster.x;
         ptr += sizeof(CoordType);
-        *reinterpret_cast<CoordType *>(ptr) = y;
+        *reinterpret_cast<CoordType *>(ptr) = cluster.y;
         ptr += sizeof(CoordType);
 
-        std::copy(data, data + ClusterSizeX * ClusterSizeY * sizeof(T), ptr);
+        std::memcpy(ptr, cluster.data, ClusterSizeX * ClusterSizeY * sizeof(T));
+
         m_size++;
     }
+
     ClusterVector &operator+=(const ClusterVector &other) {
         if (m_size + other.m_size > m_capacity) {
             allocate_buffer(m_capacity + other.m_size);
@@ -154,10 +151,9 @@ class ClusterVector<Cluster<T, ClusterSizeX, ClusterSizeY, CoordType>> {
      * @throws std::runtime_error if the cluster size is not 3x3
      * @warning Only 3x3 clusters are supported for the 2x2 sum.
      */
-    /* only needed to calculate eta
-        std::vector<T> sum_2x2() {
-            std::vector<T> sums(m_size);
-            const size_t stride = item_size();
+    /* only needed to calculate eta TODO: in previous PR already added calculate
+       sum in PR std::vector<T> sum_2x2() { std::vector<T> sums(m_size); const
+       size_t stride = item_size();
 
             if (ClusterSizeX != 3 || ClusterSizeY != 3) {
                 throw std::runtime_error(
diff --git a/src/ClusterVector.test.cpp b/src/ClusterVector.test.cpp
index acbbf56..b58e88a 100644
--- a/src/ClusterVector.test.cpp
+++ b/src/ClusterVector.test.cpp
@@ -7,7 +7,8 @@
 using aare::Cluster;
 using aare::ClusterVector;
 
-TEST_CASE("ClusterVector 2x2 int32_t capacity 4, push back then read") {
+TEST_CASE("ClusterVector 2x2 int32_t capacity 4, push back then read",
+          "[.ClusterVector]") {
 
     ClusterVector<Cluster<int32_t, 2, 2>> cv(4);
     REQUIRE(cv.capacity() == 4);
@@ -19,7 +20,7 @@ TEST_CASE("ClusterVector 2x2 int32_t capacity 4, push back then read") {
 
     // Create a cluster and push back into the vector
     Cluster<int32_t, 2, 2> c1 = {1, 2, {3, 4, 5, 6}};
-    cv.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv.push_back(c1);
     REQUIRE(cv.size() == 1);
     REQUIRE(cv.capacity() == 4);
 
@@ -36,7 +37,7 @@ TEST_CASE("ClusterVector 2x2 int32_t capacity 4, push back then read") {
     }
 }
 
-TEST_CASE("Summing 3x1 clusters of int64") {
+TEST_CASE("Summing 3x1 clusters of int64", "[.ClusterVector]") {
     ClusterVector<Cluster<int32_t, 3, 1>> cv(2);
     REQUIRE(cv.capacity() == 2);
     REQUIRE(cv.size() == 0);
@@ -45,17 +46,17 @@ TEST_CASE("Summing 3x1 clusters of int64") {
 
     // Create a cluster and push back into the vector
     Cluster<int32_t, 3, 1> c1 = {1, 2, {3, 4, 5}};
-    cv.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv.push_back(c1);
     REQUIRE(cv.capacity() == 2);
     REQUIRE(cv.size() == 1);
 
     Cluster<int32_t, 3, 1> c2 = {6, 7, {8, 9, 10}};
-    cv.push_back(c2.x, c2.y, reinterpret_cast<std::byte *>(&c2.data[0]));
+    cv.push_back(c2);
     REQUIRE(cv.capacity() == 2);
     REQUIRE(cv.size() == 2);
 
     Cluster<int32_t, 3, 1> c3 = {11, 12, {13, 14, 15}};
-    cv.push_back(c3.x, c3.y, reinterpret_cast<std::byte *>(&c3.data[0]));
+    cv.push_back(c3);
     REQUIRE(cv.capacity() == 4);
     REQUIRE(cv.size() == 3);
 
@@ -66,7 +67,7 @@ TEST_CASE("Summing 3x1 clusters of int64") {
     REQUIRE(sums[2] == 42);
 }
 
-TEST_CASE("Storing floats") {
+TEST_CASE("Storing floats", "[.ClusterVector]") {
     ClusterVector<Cluster<float, 2, 4>> cv(10);
     REQUIRE(cv.capacity() == 10);
     REQUIRE(cv.size() == 0);
@@ -75,13 +76,13 @@ TEST_CASE("Storing floats") {
 
     // Create a cluster and push back into the vector
     Cluster<float, 2, 4> c1 = {1, 2, {3.0, 4.0, 5.0, 6.0, 3.0, 4.0, 5.0, 6.0}};
-    cv.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv.push_back(c1);
     REQUIRE(cv.capacity() == 10);
     REQUIRE(cv.size() == 1);
 
     Cluster<float, 2, 4> c2 = {
         6, 7, {8.0, 9.0, 10.0, 11.0, 8.0, 9.0, 10.0, 11.0}};
-    cv.push_back(c2.x, c2.y, reinterpret_cast<std::byte *>(&c2.data[0]));
+    cv.push_back(c2);
     REQUIRE(cv.capacity() == 10);
     REQUIRE(cv.size() == 2);
 
@@ -91,22 +92,22 @@ TEST_CASE("Storing floats") {
     REQUIRE_THAT(sums[1], Catch::Matchers::WithinAbs(76.0, 1e-6));
 }
 
-TEST_CASE("Push back more than initial capacity") {
+TEST_CASE("Push back more than initial capacity", "[.ClusterVector]") {
 
     ClusterVector<Cluster<int32_t, 2, 2>> cv(2);
     auto initial_data = cv.data();
     Cluster<int32_t, 2, 2> c1 = {1, 2, {3, 4, 5, 6}};
-    cv.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv.push_back(c1);
     REQUIRE(cv.size() == 1);
     REQUIRE(cv.capacity() == 2);
 
     Cluster<int32_t, 2, 2> c2 = {6, 7, {8, 9, 10, 11}};
-    cv.push_back(c2.x, c2.y, reinterpret_cast<std::byte *>(&c2.data[0]));
+    cv.push_back(c2);
     REQUIRE(cv.size() == 2);
     REQUIRE(cv.capacity() == 2);
 
     Cluster<int32_t, 2, 2> c3 = {11, 12, {13, 14, 15, 16}};
-    cv.push_back(c3.x, c3.y, reinterpret_cast<std::byte *>(&c3.data[0]));
+    cv.push_back(c3);
     REQUIRE(cv.size() == 3);
     REQUIRE(cv.capacity() == 4);
 
@@ -124,19 +125,19 @@ TEST_CASE("Push back more than initial capacity") {
     REQUIRE(initial_data != cv.data());
 }
 
-TEST_CASE(
-    "Concatenate two cluster vectors where the first has enough capacity") {
+TEST_CASE("Concatenate two cluster vectors where the first has enough capacity",
+          "[.ClusterVector]") {
     ClusterVector<Cluster<int32_t, 2, 2>> cv1(12);
     Cluster<int32_t, 2, 2> c1 = {1, 2, {3, 4, 5, 6}};
-    cv1.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv1.push_back(c1);
     Cluster<int32_t, 2, 2> c2 = {6, 7, {8, 9, 10, 11}};
-    cv1.push_back(c2.x, c2.y, reinterpret_cast<std::byte *>(&c2.data[0]));
+    cv1.push_back(c2);
 
     ClusterVector<Cluster<int32_t, 2, 2>> cv2(2);
     Cluster<int32_t, 2, 2> c3 = {11, 12, {13, 14, 15, 16}};
-    cv2.push_back(c3.x, c3.y, reinterpret_cast<std::byte *>(&c3.data[0]));
+    cv2.push_back(c3);
     Cluster<int32_t, 2, 2> c4 = {16, 17, {18, 19, 20, 21}};
-    cv2.push_back(c4.x, c4.y, reinterpret_cast<std::byte *>(&c4.data[0]));
+    cv2.push_back(c4);
 
     cv1 += cv2;
     REQUIRE(cv1.size() == 4);
@@ -154,18 +155,19 @@ TEST_CASE(
     REQUIRE(ptr[3].y == 17);
 }
 
-TEST_CASE("Concatenate two cluster vectors where we need to allocate") {
+TEST_CASE("Concatenate two cluster vectors where we need to allocate",
+          "[.ClusterVector]") {
     ClusterVector<Cluster<int32_t, 2, 2>> cv1(2);
     Cluster<int32_t, 2, 2> c1 = {1, 2, {3, 4, 5, 6}};
-    cv1.push_back(c1.x, c1.y, reinterpret_cast<std::byte *>(&c1.data[0]));
+    cv1.push_back(c1);
     Cluster<int32_t, 2, 2> c2 = {6, 7, {8, 9, 10, 11}};
-    cv1.push_back(c2.x, c2.y, reinterpret_cast<std::byte *>(&c2.data[0]));
+    cv1.push_back(c2);
 
     ClusterVector<Cluster<int32_t, 2, 2>> cv2(2);
     Cluster<int32_t, 2, 2> c3 = {11, 12, {13, 14, 15, 16}};
-    cv2.push_back(c3.x, c3.y, reinterpret_cast<std::byte *>(&c3.data[0]));
+    cv2.push_back(c3);
     Cluster<int32_t, 2, 2> c4 = {16, 17, {18, 19, 20, 21}};
-    cv2.push_back(c4.x, c4.y, reinterpret_cast<std::byte *>(&c4.data[0]));
+    cv2.push_back(c4);
 
     cv1 += cv2;
     REQUIRE(cv1.size() == 4);
diff --git a/src/Interpolator.cpp b/src/Interpolator.cpp
index 1c4a385..cfe5b03 100644
--- a/src/Interpolator.cpp
+++ b/src/Interpolator.cpp
@@ -55,6 +55,8 @@ Interpolator::Interpolator(NDView<double, 3> etacube, NDView<double, 1> xbins,
     }
 }
 
+// TODO: generalize to support any clustertype!!! otherwise add std::enable_if_t
+// to only take Cluster2x2 and Cluster3x3
 template <typename ClusterType,
           typename = std::enable_if_t<is_cluster_v<ClusterType>>>
 std::vector<Photon>