Ok, I've finally got the arse end together after a couple of days of fidgeting. I cut notches in the rear collet (the red line) so I wouldn't have to shave off the ridges on the stock tube support (green lines) in case I threw a full stock on there sometime.
To fit the battery and wires, I cut the rear tube down about 5/8 of an inch, but you'll notice in the last pic it wasn't quite enough to seat the outer tube completely... I took another 3/8 off and it was fine.
And if you do have to do this, remember, it's worth the time to disassemble everything so you don't get aluminum pixey dust all in your mechbox. Also, sand down the edges that are left so they don't slice your battery wires. Wrap the end in electrical tape if you have to. Better safe than having your gun smoking out in the field......
Other than the grip I suppose thats about it... We'll see you at the next
Zombie Game!