All great engine recommendations. My 2 cents -- Tower .75 for power and price just can't be beat! I have a Super Sportster 60 with a Tower .75. About 100 or so flights on it. Other than an occassional click-click on the needle (probably needs to be cleaned) about every 20 flights. She just runs and runs. It turns a 12x8 at about 15,500 and can start with a flip. She has survived a wicked crash that tore the muffler off and broke off half of the rear muffler mount. Drilled and re-tapped. After dis-assemblying to remove the 1/2lb of top soil she ate it didn't even phase her (that was after about 10 flights -- and I know -- you're supposed to throttle back if your going to hit, but at 90MPH there just wasn't time).

I also have had good luck with Super Tigre and am still out on an SK50 (lots of power but low RPMs for a 2-Stroke). We have lots of guys at the field who fly nothing but OS. They are certainly great engines. But when an OS .61FX is $169.99 and the Tower .75 is $94.99 and is 0.6oz ligter with 0.3 BHP more power???? Well I'd rather spend that $75 on something else.