Saito 62 is the best engine for this bipe....OS 70 Surpass is too heavy and big... Don't hesitate for rudder authority...If you are flying with a trainer ,you can fly with it easly...If you looked ground looping effects ,you must check the both wing incidence first and C.G. second...I made it circa 89...It was powered by OS 45 FSR ,it's very well flying characteristics ,it's smooth flier...Make it light,fly with it like delight...