Actually, if pure top end speed is what you are after, the fastest is a single blade prop with a counterbalance on the other side. We all get into retreating blade stall (the blade has to bite into turbulent air caused by the passage of the blade in front of it), but that is more evident on a helicopter than on a model airplane prop, even though the problem is there. If you will send me a pm with your phone number, I will call and try to help you. You are just 10 miles down the road in Eustis.

Bill, AMA 4720
WACO Brotherhood #1