Mine is the PMC version. The top cover on the foreguard where the second battery goes is a PIA to get on and off… but don’t hold me to it, I think it doesn’t need to come off separately if you pull the hinge pin out. Then the whole front should just slide off once you take out the 6 screws above the magazine.
On the PMC the battery can go into the buttstock or the front… not sure if the wiring is in parallel or series, so it might be able to run both batteries at the same time.
I have to pull mine apart again… forgot to Loctite the piston head screw… and might JB weld the rack in place.