I have a 50SS (ringed) with an 11.25 x 3.75 prop on a 40-sized Mojo profile. It has great throttle response and pulls out of a hover with authority. Unfortunately I don't have RPM numbers. I also have a 50CX non-ringed. They are very similar in power. The 50CX is supposed to be slightly more powerful, although I don't see much difference.