A 6-7 lb Cap with a .81 4 stroke?? I wouldn't do it. I would go with a .91 4 stoke. Thats just me though. A 81-82 4 stroke would fly it just fine, just without a lot of authority. Saito's are a little lighter, but both engines are great. The longer stoke Saito .91 for $10 more than the .82 would be my choice.

If you do go with a bigger engine, move the battery pack toward to tail to balance. DO NOT ADD WEIGHT to balance.