If my sources are correct, then 216 rounds were carried. This would mean that they would have to store 18 boxes (12 rounds each) into that vehicle.
That would leave very little space for anything else.
Looking at the pictures I see a crewmember sitting in the rear at the driversside, but I also see crew standing on the passengerside next to the gun.
I have no idea how large the crew was, but Im guessing it would be 3.
I ran into the same kind of problem looking at the 250/8 and I came up with a interior layout that would seem to fit better than what I saw so far.
In this I moved the ammolocker into the right front, instead of the seat. The radio was moved to the leftside, just behind the driversseat. For the crew I added 2 foldable seats.
This way the original locker in the right rear could be maintained in order to stow vehicle- and crewgear.
Here's my halftrackforum:
http://halbketten.forumotion.com/index.htm