"Headway 38120 lithium iron phosphate cells"

They're not the burny type you're thinking of. Less volatile.

I'd rather it behind my head than in my lap for sure.

Considering how small it is - there is nowhere else to move the battery to.

If you want to keep the vehicle compact and maneuverable (and less prone to tip over), you keep the battery where it is now: low and near the centre of mass (or you can basically sit on top of it)).