diff --git a/package/android/CMakeLists.txt b/package/android/CMakeLists.txt
index 185f19e0..d1519933 100644
--- a/package/android/CMakeLists.txt
+++ b/package/android/CMakeLists.txt
@@ -23,7 +23,6 @@ add_library(
         ../cpp/Surface.cpp
         ../cpp/SurfaceProvider.cpp
         ../cpp/Listener.cpp
-        ../cpp/jsi/JsiTypeTraits.cpp
         ../cpp/jsi/HybridObject.cpp
         ../cpp/jsi/Promise.cpp
         ../cpp/core/EngineWrapper.cpp
diff --git a/package/cpp/FilamentProxy.cpp b/package/cpp/FilamentProxy.cpp
index 3d5a0963..dcb8f57d 100644
--- a/package/cpp/FilamentProxy.cpp
+++ b/package/cpp/FilamentProxy.cpp
@@ -9,7 +9,6 @@
 #include <memory>
 #include <string>
 #include <vector>
-#include "core/EngineWrapper.h"
 
 namespace margelo {
 
@@ -47,14 +46,12 @@ jsi::Value FilamentProxy::get(jsi::Runtime& runtime, const jsi::PropNameID& prop
     if (name == "createEngine") {
         return jsi::Function::createFromHostFunction(
                 runtime, jsi::PropNameID::forUtf8(runtime, "createEngine"), 1,
-                [this](jsi::Runtime& runtime, const jsi::Value& thisValue, const jsi::Value* arguments, size_t count) -> jsi::Value {
+                [](jsi::Runtime& runtime, const jsi::Value& thisValue, const jsi::Value* arguments, size_t count) -> jsi::Value {
                     if (count != 1) {
                         [[unlikely]];
                         throw jsi::JSError(runtime, "createEngine: Expected 1 argument(s), but received " + std::to_string(count) + "!");
                     }
                     std::string backend = arguments[0].asString(runtime).utf8(runtime);
-                    // TODO: Parse backend from string
-                    EngineWrapper engine(filament::Engine::Backend::OPENGL);
 
                     return jsi::Value(13);
                 });
diff --git a/package/cpp/core/EngineWrapper.cpp b/package/cpp/core/EngineWrapper.cpp
index 6220ee3e..19e63d46 100644
--- a/package/cpp/core/EngineWrapper.cpp
+++ b/package/cpp/core/EngineWrapper.cpp
@@ -21,7 +21,7 @@ EngineWrapper::~EngineWrapper() {
 }
 
 void EngineWrapper::loadHybridMethods() {
-    registerHybridMethod("test", &EngineWrapper::testHybrid, this);
+    registerHybridMethod("setSurfaceProvider", &EngineWrapper::setSurfaceProvider, this);
 }
 
 void EngineWrapper::setSurfaceProvider(std::shared_ptr<SurfaceProvider> surfaceProvider) {
diff --git a/package/cpp/jsi/HybridObject.cpp b/package/cpp/jsi/HybridObject.cpp
index 3f403a12..30139513 100644
--- a/package/cpp/jsi/HybridObject.cpp
+++ b/package/cpp/jsi/HybridObject.cpp
@@ -57,46 +57,6 @@ std::vector<jsi::PropNameID> HybridObject::getPropertyNames(facebook::jsi::Runti
     return result;
 }
 
-template<typename Derived, typename ReturnType, typename... Args>
-void HybridObject::registerHybridMethod(std::string name,
-                                        ReturnType(Derived::*method)(Args...),
-                                        Derived* derivedInstance) {
-    if (_methods.count(name) > 0) {
-        [[unlikely]];
-        throw std::runtime_error("Cannot add Hybrid Method \"" + name + "\" - a method with that name already exists!");
-    }
-
-    // TODO(marc): Use std::shared_ptr<T> instead of T* to keep a strong reference of derivedClass.
-    auto func = [this, derivedInstance, method](jsi::Runtime &runtime,
-                                                const jsi::Value &thisVal,
-                                                const jsi::Value *args,
-                                                size_t count) -> jsi::Value {
-        if constexpr (std::is_same_v<ReturnType, void>) {
-            callMethod(derivedInstance, method, runtime, args, std::index_sequence_for<Args...>{});
-            return jsi::Value::undefined();
-        } else {
-            ReturnType result = callMethod(derivedInstance, method, runtime, args, std::index_sequence_for<Args...>{});
-            return jsi::Value(result);
-        }
-    };
-    _methods[name] = HybridFunction {
-        .function = func,
-        .parameterCount = sizeof...(Args)
-    };
-}
-
-template<typename ClassType, typename ReturnType, typename... Args, size_t... Is>
-ReturnType HybridObject::callMethod(ClassType* obj,
-                                    ReturnType(ClassType::*method)(Args...),
-                                    jsi::Runtime& runtime,
-                                    const jsi::Value* args,
-                                    std::index_sequence<Is...>) {
-    return (obj->*method)(convertArgument<Args>(runtime, args[Is])...);
-}
 
-template<typename ArgType>
-ArgType HybridObject::convertArgument(jsi::Runtime& runtime, const jsi::Value& arg) {
-    return JSIConverter<ArgType>::fromJSI(runtime, arg);
-}
 
 } // margelo
\ No newline at end of file
diff --git a/package/cpp/jsi/HybridObject.h b/package/cpp/jsi/HybridObject.h
index 72cc35db..82eddf3a 100644
--- a/package/cpp/jsi/HybridObject.h
+++ b/package/cpp/jsi/HybridObject.h
@@ -8,6 +8,7 @@
 #include <memory>
 #include <unordered_map>
 #include <jsi/jsi.h>
+#include "JSIConverter.h"
 
 namespace margelo {
 
@@ -48,18 +49,46 @@ class HybridObject: public jsi::HostObject {
     std::unordered_map<jsi::Runtime*, std::unordered_map<std::string, std::shared_ptr<jsi::Function>>> _functionCache;
 
 private:
-    template<typename ArgType>
-    ArgType convertArgument(jsi::Runtime& runtime, const jsi::Value& arg);
-
     template<typename ClassType, typename ReturnType, typename... Args, size_t... Is>
-    ReturnType callMethod(ClassType* obj,
+    jsi::Value callMethod(ClassType* obj,
                           ReturnType(ClassType::*method)(Args...),
                           jsi::Runtime& runtime,
                           const jsi::Value* args,
-                          std::index_sequence<Is...>);
+                          std::index_sequence<Is...>) {
+        if constexpr (std::is_same_v<ReturnType, void>) {
+            (obj->*method)(JSIConverter<Args>::fromJSI(runtime, args[Is])...);
+            return jsi::Value::undefined();
+        } else {
+            ReturnType result = (obj->*method)(JSIConverter<Args>::fromJSI(runtime, args[Is])...);
+            return JSIConverter<ReturnType>::toJSI(runtime, result);
+        }
+    }
+
 protected:
     template<typename Derived, typename ReturnType, typename... Args>
-    void registerHybridMethod(std::string name, ReturnType(Derived::*method)(Args...), Derived* derivedInstance);
+    void registerHybridMethod(std::string name,
+                              ReturnType(Derived::*method)(Args...),
+                              Derived* derivedInstance) {
+        if (_methods.count(name) > 0) {
+            throw std::runtime_error("Cannot add Hybrid Method \"" + name + "\" - a method with that name already exists!");
+        }
+
+        // TODO(marc): Use std::shared_ptr<T> instead of T* to keep a strong reference of derivedClass.
+        auto func = [this, derivedInstance, method](jsi::Runtime &runtime,
+                                                    const jsi::Value &thisVal,
+                                                    const jsi::Value *args,
+                                                    size_t count) -> jsi::Value {
+            return callMethod(derivedInstance,
+                              method,
+                              runtime,
+                              args,
+                              std::index_sequence_for<Args...>{});
+        };
+        _methods[name] = HybridFunction {
+                .function = func,
+                .parameterCount = sizeof...(Args)
+        };
+    }
 };
 
 } // margelo
diff --git a/package/cpp/jsi/JSIConverter.h b/package/cpp/jsi/JSIConverter.h
index 727b3543..638e8270 100644
--- a/package/cpp/jsi/JSIConverter.h
+++ b/package/cpp/jsi/JSIConverter.h
@@ -20,6 +20,10 @@ struct JSIConverter {
         static_assert(always_false<ArgType>::value, "This type is not supported by the JSIConverter!");
         return ArgType();
     }
+    static jsi::Value toJSI(jsi::Runtime&, ArgType) {
+        static_assert(always_false<ArgType>::value, "This type is not supported by the JSIConverter!");
+        return jsi::Value::undefined();
+    }
 
 private:
     template<typename>
@@ -31,6 +35,9 @@ struct JSIConverter<int> {
     static int fromJSI(jsi::Runtime&, const jsi::Value& arg) {
         return static_cast<int>(arg.asNumber());
     }
+    static jsi::Value toJSI(jsi::Runtime&, int arg) {
+        return jsi::Value(arg);
+    }
 };
 
 template<>
@@ -38,6 +45,9 @@ struct JSIConverter<double> {
     static double fromJSI(jsi::Runtime&, const jsi::Value& arg) {
         return arg.asNumber();
     }
+    static jsi::Value toJSI(jsi::Runtime&, double arg) {
+        return jsi::Value(arg);
+    }
 };
 
 template<>
@@ -45,6 +55,9 @@ struct JSIConverter<int64_t> {
     static double fromJSI(jsi::Runtime& runtime, const jsi::Value& arg) {
         return arg.asBigInt(runtime).asInt64(runtime);
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, int64_t arg) {
+        return jsi::BigInt::fromInt64(runtime, arg);
+    }
 };
 
 template<>
@@ -52,6 +65,9 @@ struct JSIConverter<uint64_t> {
     static double fromJSI(jsi::Runtime& runtime, const jsi::Value& arg) {
         return arg.asBigInt(runtime).asUint64(runtime);
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, uint64_t arg) {
+        return jsi::BigInt::fromUint64(runtime, arg);
+    }
 };
 
 template<>
@@ -59,6 +75,9 @@ struct JSIConverter<bool> {
     static bool fromJSI(jsi::Runtime&, const jsi::Value& arg) {
         return arg.asBool();
     }
+    static jsi::Value toJSI(jsi::Runtime&, bool arg) {
+        return jsi::Value(arg);
+    }
 };
 
 template<>
@@ -66,6 +85,9 @@ struct JSIConverter<std::string> {
     static std::string fromJSI(jsi::Runtime& runtime, const jsi::Value& arg) {
         return arg.asString(runtime).utf8(runtime);
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, const std::string& arg) {
+        return jsi::String::createFromUtf8(runtime, arg);
+    }
 };
 
 template<typename ElementType>
@@ -82,6 +104,14 @@ struct JSIConverter<std::vector<ElementType>> {
         }
         return vector;
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, std::vector<ElementType>& vector) {
+        jsi::Array array(runtime, vector.size());
+        for (size_t i = 0; i < vector.size(); i++) {
+            jsi::Value value = JSIConverter<ElementType>::toJSI(runtime, vector[i]);
+            array.setValueAtIndex(runtime, i, std::move(value));
+        }
+        return array;
+    }
 };
 
 template<typename ValueType>
@@ -99,6 +129,15 @@ struct JSIConverter<std::unordered_map<std::string, ValueType>> {
         }
         return map;
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, std::unordered_map<std::string, ValueType>& map) {
+        jsi::Object object(runtime);
+        for (const auto& pair : map) {
+            jsi::Value value = JSIConverter<ValueType>::toJSI(runtime, pair.second);
+            jsi::String key = jsi::String::createFromUtf8(runtime, pair.first);
+            object.setProperty(runtime, key, std::move(value));
+        }
+        return object;
+    }
 };
 
 template<typename T>
@@ -112,6 +151,9 @@ struct JSIConverter<T, std::enable_if_t<is_shared_ptr_to_host_object<T>::value>>
     static T fromJSI(jsi::Runtime& runtime, const jsi::Value& arg) {
         return arg.asObject(runtime).asHostObject<typename T::element_type>(runtime);
     }
+    static jsi::Value toJSI(jsi::Runtime& runtime, T& arg) {
+        return jsi::Object::createFromHostObject(runtime, arg);
+    }
 };
 
 } // margelo