Well, I tried out an APC 11x12 "Pattern" prop this weekend. My Saito .91 turned this prop 9550 rpm when richened for flight.

The result - 90+ MPH cruising at WOT, easily 100+ while diving. Vertical is not unlimited, but there's plenty. This prop is actually a lighter load on the engine as it unloads quite a bit in the air. I can't even describe how smoothly it runs whilke at speed!

The downside? Very strong P-factor which increases while accelerating. The plane will pull slightly to the left, which made it a little more difficult to fly traditional oval race lines... had to trim in a little rudder to counteract. Forget about prop braking effect. We had minimal wind yesterday, and all my landings except one went long.

It also isn't a real "thrusty" prop. The plane was more aerobatic at lower speeds with the bigger diameter prop. No surprise there.

The verdict? I'm keeping this prop handy for windy days, and will try a 13x7 / 12x8 for calm days.