To respond to your original post; OS manufactures and sells engines in many areas that have very low noise limits. To keep the noise down, OS recommends props that limit the engine's rpm. If you tried your engine with the largest recommended 2 blade prop, you would also see about 8500 rpm. To reach 11,000 on that engine you would need a 2 blade of a size of about 12 x 8 or 13 x 6. Or a 3 blade of about 11 x 8 or 12 x 6.

I have used 3 blades on several airplanes, either for ground/water/airframe clearance or because they are cool. Also, at higher rpms, they make an awesome "singing" noise. But no, they do not make more thrust than the equivalent 2 blade (1 inch less diameter) and they will not turn faster.

Jim