Scott,

The recommended prop size for this engine is a 9x5~6, 9.5x5, or a 10x5. Of course the 9x5 will get you in the high rpm, however it will suck approx. 2oz./min. of fuel. Go to www.os-eingines.co.jp and print or download the manual.

I have two of these and haven't yet flown them. I just picked up a Pica .26 size P-51 kit. The engine fits inside the cowl but not all the way forward. I plan to mount the engine on the firewall and manufacture a prop hub extension. The Sportsman Aviation Waco .30 ARF biplane probably would have been a better choice considering the light wing loading to carry extra fuel and the engine fitting inside the cowl without any modifications. I'll give it a shot anyway. If the old lady lets, I might get the Waco to put the other engine in.

What do you plan on mounting the engine on?