I have the GP Cap with an OS 70 in it. I would reccomend the APC 13X6 Prop for that plane. You will end up with tons of power and great vertical. The best motor for the plane is the OS .91 Surpass II. It has the same weight as the .70 +- a tiny bit and fits perfectly. A friend of mine went with the .91 combo and it is great. I did all the maiden flight stuff for him and found it much more enjoyable to fly than with the .70. His goes straight up with power to spare. His has an APC 15X6 prop and it turns that great. Dont under prop a 4 stroke! Very bad! Go with the 13X6 if you already have the .70. Should turn it at about 10K on 15% fuel.

Good Luck, Phil (Mesa, AZ)

By the way, mine came in at 5.5 LBS with the OS .70 Surpass II and NO modifications.