RE: OS 35 AX Breakin
A 10 x 6 propeller won't over-rev a .35-size engine. When you lower the RPM, you are lowering the performance of the engine. Can't help that. The "correct" propeller is one that will allow the engine to turn in the middle-12,000's at full-throttle on the ground and still fly your airplane the way you want it to fly.