I'll just toss my 2 cents in and say...
I saw 10,300 R.P.M. w/ a 14X6 APC leaned right out, and then I richen it to about 9,800 give or take a few, for flight.
(that's with PM 15% fuel, O.S. type F plug )

Mine's in a H9 P-40 and flys it quite well...actually a little fast to be scale speed, but...