My LA and FP .15s are on hand launch planes and the motors work flawlessly. I guess I don't tilt them up like a taildragger. I have to cut the motors at the last minute with the trim so the props are not spinning into the dirt. I would guess 3.500 ripems though. Most of the mufflers I have bored out the baffle and opened up the muffler outlet. That would not be the right thing to do for a reliable idle. You could also experiment with just taking off the muffler pressure tube and richening it just to see if it makes it worse. (I would guess that it does, but it is free to try it out.)