diff --git a/build.gradle b/build.gradle
index 7a59b1b..efe0bf1 100644
--- a/build.gradle
+++ b/build.gradle
@@ -11,18 +11,47 @@ javafx {
 }
 
 version = sharedVersion
+sourceCompatibility = 17
 
 dependencies {
     implementation project(':MCU-API')
     implementation project(':MCU-DownloadLib')
     implementation project(':PackBuilder')
+
     implementation 'com.mojang:authlib:1.6.25'
+
+    runtimeOnly project(':MCU-ForgeLoader')
+    runtimeOnly project(':MCU-ForgeLoaderV2')
 }
 
 application {
     mainClass = 'org.mcupdater.gui.javafx.Main'
 }
 
+def testMCURoot = "c:\\Users\\"+System.properties['user.name']+"\\MCU-Test"
+run.doFirst {
+    // provide default args if we're running via gradle
+    if( args.size() == 0 ) {
+        mkdir(testMCURoot)
+        args = [
+                "-ServerPack", "http://files.mcupdater.com/official_packs/mcu-1.16.5-together.xml",
+                "-MCURoot", testMCURoot,
+                "--runtimes=8#c:\\temp\\jdk8u302-b08-jre\\bin\\java.exe;11#c:\\temp\\jdk-11.0.12+7-jre\\bin\\java.exe;17#c:\\temp\\jdk-17+35\\bin\\java.exe",
+        ]
+
+        // make sure we have current forgeloader jars
+        copyForgeLoaders
+    }
+}
+tasks.register("copyForgeLoaders", Copy) {
+    def dest = mkdir(testMCURoot + "\\lib" )
+
+    from file("..\\MCU-ForgeLoader\\build\\libs\\MCU-ForgeLoader.jar"),
+         file("..\\MCU-ForgeLoaderV2\\build\\libs\\MCU-ForgeLoaderV2.jar"),
+         file("..\\MCU-LegacyForgeLoader\\build\\libs\\MCU-LegacyForgeLoader.jar")
+    into dest
+}
+
 processResources {
     duplicatesStrategy = DuplicatesStrategy.INCLUDE
     from(sourceSets*.resources.srcDirs) {
diff --git a/src/main/java/org/mcupdater/gui/javafx/Main.java b/src/main/java/org/mcupdater/gui/javafx/Main.java
index d80267b..3f41b6b 100644
--- a/src/main/java/org/mcupdater/gui/javafx/Main.java
+++ b/src/main/java/org/mcupdater/gui/javafx/Main.java
@@ -52,10 +52,17 @@ public void start(Stage stage) throws Exception {
 			}
 		} else {
 			newProfile = settings.findProfile(settings.getLastProfile());
+			// if no 'last profile' was saved, just default to the first one in the list
+			if (newProfile == null) {
+				newProfile = settings.getProfiles().get(0);
+			}
 		}
 		controller.refreshInstanceList();
 		controller.refreshProfiles();
-		controller.profiles.setSelectedProfile(newProfile.getName());
+		// if no profile is set, avoid npe on the name lookup
+		if (newProfile != null) {
+			controller.profiles.setSelectedProfile(newProfile.getName());
+		}
 	}
 	
 	public Image getImage(String filename) {
diff --git a/src/main/java/org/mcupdater/gui/javafx/MainController.java b/src/main/java/org/mcupdater/gui/javafx/MainController.java
index b4da0ce..3aaa985 100644
--- a/src/main/java/org/mcupdater/gui/javafx/MainController.java
+++ b/src/main/java/org/mcupdater/gui/javafx/MainController.java
@@ -394,7 +394,13 @@ private void tryNewLaunch(ServerList selected, List<ModuleEntry> modules, Profil
         }
         String playerName = launchProfile.getName();
         String sessionKey = launchProfile.getSessionKey(this);
+
+        MCUpdater mcu = MCUpdater.getInstance();
+        Path instancePath = mcu.getInstanceRoot().resolve(selected.getServerId());
+        // NB: we want to use the loader's version json for arguments if one exists
+        MinecraftVersion loaderVersion = MinecraftVersion.loadLocalVersion(instancePath.toFile(), selected.getLoaderVersion());
         MinecraftVersion mcVersion = MinecraftVersion.loadVersion(selected.getVersion());
+
         selected.getLoaders().sort(new OrderComparator());
         String indexName = mcVersion.getAssets();
         if (indexName == null) {
@@ -409,8 +415,6 @@ private void tryNewLaunch(ServerList selected, List<ModuleEntry> modules, Profil
             clArgs = new StringBuilder();
         }
         List<String> libs = new ArrayList<>();
-        MCUpdater mcu = MCUpdater.getInstance();
-        Path instancePath = mcu.getInstanceRoot().resolve(selected.getServerId());
         File indexesPath = mcu.getArchiveFolder().resolve("assets").resolve("indexes").toFile();
         File indexFile = new File(indexesPath, indexName + ".json");
         String json;
@@ -442,7 +446,12 @@ private void tryNewLaunch(ServerList selected, List<ModuleEntry> modules, Profil
         args.add("-Xms" + settings.getMinMemory());
         args.add("-Xmx" + settings.getMaxMemory());
         //args.add("-XX:PermSize=" + settings.getPermGen());
+        if (loaderVersion != null && !loaderVersion.getJVMArguments().isEmpty()) {
+            clArgs.append(" ");
+            clArgs.append(loaderVersion.getJVMArguments());
+        }
         if (!mcVersion.getJVMArguments().isEmpty()) {
+            // we may only want to try the mc version's args if we don't have one for forge?
             args.add(mcVersion.getJVMArguments());
         }
         if (!settings.getJvmOpts().isEmpty()) {
@@ -526,6 +535,9 @@ private void tryNewLaunch(ServerList selected, List<ModuleEntry> modules, Profil
         fields.put("user_properties", "{}"); //TODO: This will likely actually get used at some point.
         fields.put("user_type", (launchProfile.getStyle()));
         fields.put("version_type", mcVersion.getType());
+        fields.put("library_directory", mcu.getInstanceRoot().resolve("libraries").toString());
+        fields.put("classpath_separator", File.pathSeparator);
+        //fields.put("version_name", "minecraft"); // the filename of the jar to be executed
         String[] fieldArr = tmpclArgs.split(" ");
         for (int i = 0; i < fieldArr.length; i++) {
             fieldArr[i] = fieldReplacer.replace(fieldArr[i]);