ORIGINAL: phread59
Yes a 10-4 is small for this engine. An 11-6 would be a good place to start. If you under prop an engine you certainly can tear it up. I would look for a bigger prop. I like APC's myself. Try one in 11-6 and see how it flies. It will have a lot more power and less speed.
Mark Shuman
I was using an APC 11x6, but for some reason it was vibrating the plane way too much and I was getting bad foaming (yes, it was a balanced propr).. So we put a master airscrew 10x4 prop on it and I liked how it performed. And soundwise, the 10x4 SCREAMED.. I loved how it sounds.