My OS 91FX tachs at 9800 with a 13x10. I use for speed as well in my Minnow. I was thinking of trying a 12x10 out, but after the previous post i might try that 12x14 as well! Question, is there any guideline as to how much an engine will unload when flying, or how close to the max rpm specs of an engine you should be when taching on the ground?