There are voices that want to mandate a metal battery-support-baseplate, but for now anything is ok.

For team RCC.

LiFe's are no firehazard. We had in the 7 years we use'm 2 mishaps.
1) Recharging a 4S pack on 6S. Result, a bit of smoke and bulged packs.
2) Drilling a hole trough them. Result, a lot of smoke.

The raptors Nebelwerfer and Perun use a bend and HDPE box that gets closed up when the armor goes together.
Hannibalito 3.2 uses a steel plate with bend sides as part of a support frame, and a piece of heavy duty RC velcro strap.

These 3 machines use a Zippy 3S 4000mAh LiPo hardcase pack.

Bullfrog has a shockmounted ali box containing the 2 5S 5000mAh LiPo's.
Kan Opener has shockmounted open framed Titanium support structures to keep the 4 Zippy 4S 8000mAh packs in place.