I think it would just be heavy bays, not the heavy and light bays that replace the mech bays in a Lee, The 1200 extra tones left over would be good to keep for supplies, as most vehicles burn through fuel, ammo and armor at prodigious rates. You also have to account for all the extra passengers the vehicles require. Figure 4 or 5 on average per vehicle. I would not count out having a infantry company or even a battalion on board, though that really starts to stretch supplies, waste management and air/water recycling.