RE: Hangar 9 J-3 Piper Cub 40 arf
An O.S. 52 4-stroke (15.5 ounces) flies it adequately for scale purposes. A .70 size 4-stroke (17+ ounces) might be actually better as you would need the weight up front and the extra power would provide some margin to get out of trouble. You ARE going to use a 4-stroke aren't you!!![:@]