Quick Update

The belt for the drum arrived today from Technobots, and it's a perfect fit. No tensioners required!
Just gave it a quick spin-up and I'm happy and impressed with the brushless configuration. The drum could be a problem though.

Despite appearing to be balanced when spun by hand, it starts to vibrate and bounce considerably when the throttle goes past about 20%. I reckon this is the same issue of dynamic imbalance that Calum experienced on his drum that just had two teeth offset at 180°.
I had hoped it wouldn't be too much of an issue having three teeth at 120° intervals but seems that's not the case.

Worst case scenario, I can run it at the champs and just ramp up the throttle when I'm about to hit an opponent, but I think it's worth seeing if I can get another tooth made and add it to the drum in the same arrangement as the old drum, so: V---^---^---V

Back out to weld the armour back together, but will have some pictures and possibly a video later.