Awesome.
That's one sexy gun. As for your battery situation, if you're going with LiPo, I would recommend putting that 3-cell 1200mAH 11.1V LiPo in the stock tube to ensure it's not accidentally damaged while gaming.
Yeah, it's a bit more of a pain in the ass to swap (especially in-game), but it will ensure it's not accidentally damaged while you're playing. The gasses in LiPo batteries are very dangerous if inhaled - albeit the likely hood of a BB damaging the battery
that much is pretty bloody slim.
This is where I plan on storing the battery for my
MGS4: M4 Custom project.
Food for thought is all.