I have a .90 SP and a .58 CD, the .90 SP turns a 17X6-10 Zinger fourblade prop at 5,500 rpm and flies a H9 P51 very scale like, the .58 CD turns a 13x6 at 9,000 precisely, just as they claim. There is no risk and no mystery, they're just engines. 10% nitro fuel with 16% lube with a couple of percentage points of that being castor and a Hangar 9 SuperPlug is all that's required.