With the Clipped wing you will be under powered,
I am flying my Sig 1/4 scale C/W with a Magnum 120 and it is just about right. Anything under 1/3 throttle and it will lose altitude. It pulls it through loops just fine. I would say you will be just fine with a .91 on a full wing Cub. I have 4 hours of stick time in a full scale J-3 and when you want the plane to do anything you better be at full power. The Cub is a great flying plane no matter what the scale!!!!
Anthony