B.L. Did you mean to quote me? If so then I understand about a good battery box and using tie downs...but I also know how easy it is to rip bolts out of sheet metal etc. and I would be worried that considering in a 35mph crash (for instance, into a brick wall to keep things simple) the G forces would be ~20G's, I got that information from here:
http://forensicaccident.com/Crash%20Analysis_.htm If it was 20 G's then it would be putting an 800lb. load upon the tie downs...the tie downs that I've seen dont particularly look up to that kind of task and I worry that where they would be bolted too, which is effectively sheet metal would not be either unless you used a backing plate for each bolt. I think if I was mounting a battery in the back of my hatch I would use a 2 inch wide x1/4 inch thick piece of steel with two "legs" on either end of it. It would then be bolted through the floor to a backing plate of a similar size to the battery with 8 3/8 inch Grade 8 bolts. That thing would NEVER move
Edit: One more thing, with a battery in the back, it significantly cuts down on "fun" possible back there
