Hi,

A lot of guys prefer the larger prop and lower rpms. More static thrust and less speed. I don't fly 3D however, and prefer more speed. I also like the ability to cruise around at half throttle, with power in reserve when I do maneuvers. I used an APC 18 x 8 on mine, and the 42cc turned it at around 8400 rpms. I flew the engine for a year in this manner, so it shouldn't be a problem. If you are going to put the engine in something sleek and fast like a warbird, the engine would easily pull an 18 x 10 prop.

AV8TOR