Yes on the 666 gram batts..Although i saw some F3A guys using my exact batt packs.  .i figured i could even get away with 4000 mah packs and drop to 1250 grams but no one else seems to have to make that sacrafice.... i never considered 15C  will study that now....  The carbon wing spar and gear as well as eliminating the wheel pants will get me 300 grams.  200 dollars on carbon prop and spinner would only get me 65 grams.  All that leaves me with 1.47 lbs to cut and drill out of the airframe not sure i can get that safely.   it must be the airframe is just too heavy....