I had the Magnum 70 FS in mine, It turned a 14" prop, which is scale, but it is too much engine and too much prop. I ended up using 13X6 prop and flying the engine at 1/2 throttle, tops (including take off).

The maiden flight was memorable: at take off, the plane jumped off the ground like some 3D toy. Very uncublike! I have learned to fly it like a Cub!