I have a GP Spacewalker with a G23 (converted to CH Ignitions). Came out to around 10 lbs dry all up weight. Balances with 3 servos under the stab perfectly. Great flyer.

I would say a Ryobi on CH Ignitions would be perfect balance-wise with plenty of power to spare, though you'll have to do a main landing gear mod to clear an 18" prop.