Well you know what the first thing I did was once I had the body off. I bought these 3S packs a few weeks ago and looking at the battery box dimensions for the Outcast, I was worried they wouldn't fit. My worrying was for nothing. They are a bit long but the 2 stacked one on top of the other fit just fine! I still have some wiggle room side to side and a lot of room vertically....The length is perfect IMO.