I hav'nt gotten it yet, but I plan on building a Balsa USA stingray 120 and install an old ryobi 28cc engine I have. The Balsa USA Stingray comes in at just under 9 lbs total with a wing area of 1276 sq in. My 28cc ryobi turns a 16x8 Master airscrew prop at 7500 rpm. That should be a good combination.

Thanks