Brilliant idea, but I think that's too much ammo for a UAC. It'll jam before getting through all 10 rounds of fire... 
I wasn't sure what else to put in it, and the original carried a four ton ammo bay as well. I agree that something like this is going to attract a tremendous amount of incoming fire (most of which will miss, ha ha) so it's not likely to survive much more than its initial volley of fire anyway. Maybe three machine guns and a half ton of ammo, and two tons of UAC20 ammo - it's not designed to last long, so short ammo supplies would convince crews to shoot their wad and fall back quickly. The MGs would be useful in cities, taking on infantry in its home environment where the Hetzer works best anyway.
