I have been on the engine search for an O360 or IO360 for my RV7. I have found 2 in my price range, the first one is an A2F with solid crankshaft and the second is a A1F6 with counterweighted crankshaft. Both claim to be 0 TSMO. The A1F6 seems has new cylinders but is across the country. I am keeping it simple so it will be fixed pitch. The counterweighted crankshaft scares me a little, its adds weight and strays from the simple objective. I have found some info on pros and cons but not a lot, I am reading they do not like rapid throttle changes. Any experts on this subject out there?