It also depends on the engine. The MVVS .77 that I have on my stick is timed and tuned for lower RPM's and larger props. Putting a smaller prop with more pitch to increase speed (and proportionally RPM's) does no good because the engine is not timed to handle the higher RPM and gives poor performance. It is ported to give its best performance in its midrange not at max. RPM.
Thats why I said " a hot, high rpm engine with the right prop".