While I can only attest to the power and performance of the OS 70 Surpass II performance I would assume that an OS 91 4 stroke would be perfect. Im my Cap I would not hesitate about putting a 91 in it. In fact, if I were to do it all over again I would most likely go with the 91. The weigh difference between the 70 and the 91 is almost nothing and the .70 balanced the plane out perfectly (GP CAP kit). The little .70 runs flawlessly and is an easy to opperate engine. Going to the field and playing with the motor is not my idea of a good time. Having said that, I would go with the OS 91!

Having a lot of prop will give you the performance you are looking for and the 91 will give you just that!

Phil (Mesa, AZ)