CrashBevil,

It sounds like you have a very strong O.S. Fx engine there. Our local races use that same engine, and very few, if any, of our engines would turn a 10x8 prop at the rpm you stated.

Some of the better props we have found for that engine would be:

Sport APC 9x7
Sport APC 10x7
Pylon APC 8 3/4" x 8.5 W
Pylon APC 8.8 x 8.25
Pylon APC 9 1/2 x 7 1/2 N (My Favorite)

We use these props on Quickee airplanes, which may be a bit more streamlined than what you may be flying. You need to do some experimenting, all of these props will run differently on different days based on Temperature, Humidity, and Pressure.

A radar gun will help with proper prop selection.