[trit21]

i fear you are going about this all wrong. Props are sized not for speed but to ensure rated RPM's can be reached (many cases over rated RPMS's) at full throttle. If you are adjusting props to get more speed, you MAY be overloading the engine and this will cause damage to your engine in the form of dropped valves typically. To much heat in the exhaust which transfers to the drive train and boom. If I have missed something above, please ignore this post, if not, do yourself a favor and only pitch for ++rated RPM at WOT.