I think you are right about the 11-7.5 being too big and I went this morning to try a 11-6 but I didn't have one. Another trip to the hobby shop will solve that. I have always used Master Airscrew because they are cheap enough and pretty tough, anything better? The 10-8 does O.K once it is up but takes off like it has a load of rocks in it and loses airspeed quickly with any type of manuver. Still, the RV-4 handles pretty well. I think I will stay with the Royal regardless of the power just because of how reliable it has been.  0 dead-sticks, knock on wood!