RE: Why only OS FS in SPA?
pretty much SPA standard is Morgan Fuels Cool Power 30% heli thru the OS, with anywhere from a 13*9, 13.5*9. Turn up the nitro and she runs. The extra oil (full synthetic) keeps them cool. There are SPA members with 4-500 flights on the same set of bearings with this fuel. All applies to I and II.