Dual battery bracket???

I recently scaled the car and need to move my second battery to the passenger side to get the needed weight over there. I now need to make new battery holders. I would like to make a tandem side by side bracket and am wondering if I can use one hold down across the top for both batteries? Or do I "need" to use one hold down per battery? I don't know what NHRA says..
DC

I use two seperate trays and three 1/2" bolts w/alum strap going across both batteries w/one bolt on each end and one in the middle.....have always passed tech that way. The batts are side-by-side by the way not end-to-end.

I made one hold down bracket which fits over both my batteries and have it bolted down via two 3/8 bolts. It's made out of angle iron and is very strong.