Being flying my SS for a month + with a cheap GMS 1.20 ($129.00 at tower hobbies) a pitt muffler, a 16 x 8 APC a mix of used hitec MG servos (from my R/C cars) throws around recomended in the instruct book, CG at 4.50" to 4.75" with a 1 oz. Pratt weight on the propeller and is flying so good that two more been bought by our club members. Half throttle for pattern flight (3.3 hp - 26.5 oz engine as advertised) it's still on the light side with 10 + mns per tank (haven't stated yet exactly how mutch after 10 mns but should be 12 to 14). I think is not to bad for a big 2 stroke.