Thanks for the replies. The Magnum and ASP four strokes sound interesting. Anyone know how realiable and easy to tune these two brands are? Will they run as well as an OS AX series two stroke? I really want to focus on the engine that will give me the least hassle. If the OS 120AX requires a 17 or 16 inch prop, that's going to be problematic for ground clearance, even with the tail dragger conversion i've done.