Good luck. You would think somebody else out there would make a good set of rotating retracts for up to 15 lbs, but I havent seen it yet. Buy lots of extra parts (especially the little scissor arms) I dont think Ive ever flown more than 4 flights on my GSP corsair without bending one. But at 12+ lbs Im probbly pushing those 615's a little farther than they are designed to go