When I had the 46ax on the Tower Trainer I was using a Master Airscrew 11x5 and it was plenty fast. I have since installed that engine on my GP Big Stick (and I have yet to clean the mud out of it and make sure it's ok ) So the only engine I have left is the 40LA to go back in the Trainer. The 40 flies it fine, but it is kind of uninspiring. One of these days I'll get a bigger engine for it, but my priorities for the time being are to finish this tailwheel conversion, and then fix my Big Stik. Plus I got a Hanger 9 field box for Christmas so I need to put that together as well!! That should keep me busy for awhile! With a wife and three kids I have limited time to work on this stuff. Thank God for ARF's!