i feel comfortable when a plane is flying fast... rather than having thrust, I want revs... I have 11x9, 13x8, 14x8 and 15x6... the 14x8 and 15x6 give me below 10K rpms... and OS suggests its overpropped then... must at least be getting 10500 revs... the 13x8 does give me more, but I feel I need a bit more...