Jim, I've buitl the stingray 120 and belive it or not, flew it with a Malonet 100. It flew good but it took all the motor it had to loop. I will say you should move the firewall back some. I didnt and needed lead in the tail to balance which added to it overall weight that I think was about 11lbs. The ryobi would make it a great performer but because the ryobi hangs out from a rear mount use the 2" one. If memory serves me, I was using a 15" or 16" prop on that Maloney and still had good ground clearance for the prop. Make sure to look at that if you build one. If you talk to Peter again tell him Mike Emily sent ya.