They can wind up pretty good. My AP .09 went 15,200 on a MA 7-4" and 16,900 without the muffler. I never tried it with the F2D prop yet but my AP .15 (.135 really) was going 24,900 rpm with a bit bigger contol line carb I made, about 6 mm and on muffler pressure. I quit using that because the rod bushing was getting a lot of play in it after about three runs. The .09 has a much smaller and lighter piston so it may be ok. Never thought of making a Turbo plug head for the .09. I roughed out a few blanks. 14 I think. Just to compare-I like to do that, my OS FP .10 was 17,200, my OS LA .10 was 17,500, my Tee Dee .09 16,400 All these with no muffler, and a TT GP .10 13,500 with a muffler. because I had it in a plane and didn't want to take it off. Unfortunately the wing folded up last fall. I was heartbroken, I had it since 1990.