I don't know about your engine box, but for a prop you can run a 22x10 Bolly wood and expect right at 7,000 rpm. A mejzlik 22x10 will turn up about 300 more r's. If that's not fast enough for you, maybe drop down to a 20x12. I got a hunch you'll be pleasantly surprised with the 22x10 though. Just prop the engine so it will be in the upper 6's to low 7's on rpm and the engine will be happy....