Mine has an OS46FX on it and it is a great engine for this plane. It keeps it light and has enough power to hover if need be. Mine will pull out of a hover with 15 percent nitro and an APC 12x4 prop. A couple of guys at my club have put four stroke 70s on theirs and have commented on how well mine flys on the 46. In my opinion, the 70 FS is too much engine. Also, the landing gear has to be modified to increase the ground clearance up front when swinging a 13 or 14 inch prop. Go with the 46. Hope this helps.