Just checked out the Ryobi 31cc and it will be about 1 1/2 " too long for the cowl of the Rascal. After checking out the other suggested planes I think I will stay with SIG. Good luck in the past. It looks like I may be moving to the RCS 1.4. Seems like a real nice engine, and maybe something I can move on to the next project. Can't believe I am planning beyond a plane I don't have yet! Must be a sickness...........