Battery and Rear Bulkhead question

I understand the box, but if using the optima style battery can I secure it in a battery tray to the frame rail and not put it in an approved box and not have to install a bulkhead?
Thanks
Rod

sort of, this will require two 3/8" bolts or allthread on each with a 1/8" strap across the top of the battery and bolted to the floor with large washers or to the frame. no bulkhead needed. a fuel cell will need a bulkhead but still no battery box.