Also: the KWA G36C has the large foregrip, which can hold a large NiMH battery. This negates any reason to get a Lipo, other than the weight factor. The voltage difference between the two chemistries are negligible (voltage doesn't affect your ROF as much as current), what really matters is the current it can provide. It is true that Lipo's can output much more current than NiMH, but using a large battery the difference is negligible once again. The motor only takes what it needs (in very simple terms), so at stock mechbox settings you probably won't even notice a difference between a similar voltage Lipo and large NiMH cell battery ROF.
In my opinion Lipos are a pain in the ass, and would much rather use a large battery if given the option.
(large NiMH cell = Sub-C cell, generally 3000mah or greater)