by cutting battery weight in half and increasing volyage a few volts(18.5 lipo---16.8nimh) you could keep up with less throttle and not notice much flight time loss.a fully charged 5s lipo is closer to 20v. from what i understand each cell fully charged is close to or is 4v.
that much weight saving and increased voltage sounds sweet.im not forsure but kokam might have 3270 mah @ 20c, fmadirect.com should have that info.65+amps of moto-vation----hizzah.