I think that is a good point regarding the operational load options, but the gun bay volume (ammunition "channels" or sub-bays?) allocated to ammo for each M2 appears to be the same for any of the 8 (or 6) guns so I don't understand how the number of guns carried would have an effect on the maximum rounds per gun.
The current DCS module description and user manual (and a host of other sources) also state a maximum capacity of 425 rpg, which doesn't appear to be possible in the sim right now unless the P-47 M2s are using a higher rate of fire than the M2s in the P-51, which would be strange?
Anyway, great module. I'm having a lot of fun with it.