You're right on the nominal of a 6S lipo, but the Pack I use in my feather was the one from that 40kg and at 4000mah it drops from 25.2 (full charge) to ~24.5V in a feather fight.

The hubs appear to be aluminium, if that won't stand up to it I can probably get some go kart wheels and fix them on somehow. I was going to have the chassis have side armour for the wheels though. I'll take your advice on just getting a rolling chassis first, that'll probably be best and give me some idea of what kinda of weapon would work for me in a heavy after a bout or two