Maybe its just been at our field but the Thunder Tiger Pros and the OS Fx or the newer AX series have all been excellent. Easy to adjust and gobs of useable power. The Super Tigers have been very tricky to adjust. You spend 5 minutes tinkering, refuel, take off, fly for a minute and then the engine still quits! Happens time and time again. Almost all the ST engine owners have switched over to OS. Now they spend their time flying instead of tinkering. The carb barrel also doesn't turn smoothly right from the factory and a lot of them have suddenly suddenly jamed in 1 position. I have found other brands that also do this. I had a WM Tiger Shark 75 carb jam on me. I could barely get the barrel out of the housing to fix it. Machined it smooth and it has been a good engine. Now I check all my new engines and if it turns rough I take the barrel out and machine it smooth before installing it in the plane. The OS, and Thunder Tigers carbs have all been good right out of the box. I just bought an ASP Super Series 52 and the carb barrel turns smooth on that one as well. Haven't had a chance to try the engine out as yet so won't comment on that.[8D]