I know that in Europe............(I used to live in Scotland) that our Zenoah engine all came with graphs for power and torque against rpm. I set up my engines by propping just slightly ABOVE the torque peak. If the torque peak was 6500rpm Id prop the engine to turn 6700rpm ON THE GROUND. The STATIC rpm IS the SAME condition as when pulling from a hover.........zero airspeed maximum rpm. If I needed more power and the NOISE constraints would allow............I would prop for more rpm.

The reason for doing this is that if you are BELOW the the torque peak (below in rpm) when you meet your maximum load situation (pulling from a hover) then the engine will have no more turning force available and readily lose rpm. If you are ABOVE the torque peak (in rpm) when you meet the max load condition then the engine has more turning force available to maintain rpm.

No guesswork, no fuss, no "RIPPING THIS OR THAT PROP" .....ugh