Hi Vapelyfe001,I don't think anyone has addressed this issue yet, so I wanted to share. I know this thread is old but there may be someone who wants or needs to replace an old battery in their mod.
Cheers! Might dremel .5mm out of the back in that case!@RHV. No I didn't modify at all, was a tight squeeze to get in but went in fine. You do need to take a black bit of foam out from the inside/back of box, once battery is and you go to screw the front of mod back on make sure not to tighten too much as battery does press against the board.. hope this helps, good luck!