Again.. what are you looking for in performance? The recommended prop size wll give you one optimum RPM range and that's probably within the limits of that engine. Trying to get more out of it will actually give you less performance and more wear and tear on that engine.

Stick with the recommendations and go with the RPM you are getting. That's just fine.

Or, as I said, get a bigger engine. An OS 55 AX has the same footprint.. and will have that thing standing on its tail from the ground to the clouds without difficulty.

CGr.