I have an OS .55 (broke in with 9x6) currently running an apc 11x7. I tried to run a 12x6 today, and the rpm's just didnt seem to come up to normal. Am I trying to put too large of a prop on this thing, or is the 11x7 the best it's going to get? My general understanding is if you up the diameter, decrease the pitch by the same amount you increased the diameter. Im just trying to get a little more torque for takeoff, im not really too concerned about the top end speed. The aircraft is a 4* 40, and im running 15% nitro 18% oil Byron fuel, with an os #8 plug. Any input would help as far as the airframe goes also, the best prop for the airframe..... yadda yadda yadda.......