My SK 50 is on a heavy trainer Excel 2000(about 6 lbs.).Starts at first flip,idles great as long as you want.Transition is good.(I keep it a little rich for safety).At full throttle it pulls my heavy trainer -almost- unlimited vertical.(I couldnt test it so long to prove because I afraid to loose).Im using industrial methanol(means a lot water), full castor and 11x6 prop.Im soo happy with my cheap but flawless engine.Most of all very reliable,never had a deadstick during its about 6 hours flight time.I wonder if anybody could try it with famous Tower muffler?How about add on power with it?