Li-po batteries are very good to supply large current. I just tested "Tenergy 7.4V 900mAh, 25C High Power Lipo Pack" on Nybble. It seems that with its super power, the protection in NyBoard's step down chip will always be the bottleneck. So it's a must to bypass it as discussed in previous post . It's also recommended to design a customized battery mount to replace the original one on the belly, to keep the center of mass low and symmetric.