Hi Barry:

I was at this point a few weeks ago trying to figure out what my first gasser would be. I still don't know as I went the opposite way from you and went smaller and got a YS110! Ha ha. Anyway, there is a fellow on here whose name is Aerobob and he did a spreadsheet, located here: http://www.rcaerobats.net/GAS_ENGINE_WTS.htm which you might find helpful. I was thinkning that the Evolution 45GX would be very good, but everyone will have different tastes. Aerobob's spreadsheet shows that the weight differences between the 50cc classed engines are very minor when you consider the weight of the muffler and ignition system.