A ys 120 would be great........You dont need any larger... More wingloading on a geebee , and the more it becomes a flying brick!!! There was a guy on here that put a 30cc weedwacker in it, and on the maiden demolished it on laning due to the massive wingloading.. I would even go a satio 120....... Definatly a four banger so you can swing a larger prop around that massive fuselage.... Keep us posted.. I have been intrested in one myself.!!