Not bad Desertsfox I give you an 8/10 for Kitfox Model knowledge.

The Model three also had wooden Aileron hinge attachment points these were a continuation of the actual wing rib. The Model 4 and onwards departed from this method and employed separate metal fittings which attached to the ends of wood ribs to serve the same function.

I also understand that the later model 4 had thicker carry through tubes for the wings attachment and thus the heavy load capability. The struts on the Model 3 and 4 are the same and attached at the same point along the wings spars. The 3 and 4 are very similar in structure almost the same.
Aerodynamics and the flaperon mixer were the main differences.

I'll be happy with a 5/10