One important point here is to undersatand that the manufactuers specs list HP at a certain RPM. For the most part, this RPM is not a typical nor a nominal RPM for that engine. Smaller engines will operate at higher RPMs than larger engines.

Noise does not equal power.

Having a prop that allows a high level or RPM, although it may reach the theoritical nominal for that engine (what the manufacturer states, in other words) is usualally not a practical operating RPM for that, or any engine.

A .55, for instance may say 2.2 HP at 15000 RPM (this is not what they say, but is just an example) a practical max RPM for that engine may be 11,000 RPM. So, select a prop that will give you the best performance at that RPM.

This takes trial and error and a little time to organize the stats for your particular engine and then select the prop to work with it.

CGr.