I did, but obviously they did not get the point, simply telling me that the effects are installed into the main P3D effects folder. Which is plain stupid to have either an add-on.xml pointing to an empty or non-existent effects folder and instead installing the effects into the root directory if the plane is basically using the add-on.xml method. Sorry to say, that is just lousy coding... Fixed the add-on.xml myself by simply removing the Effects part, but come on...