So,
I'm a firm believer in lightweight AGM batteries for the S2000. I use the Odyssey PC 680 in all my cars and have done for years. Anyway, $130 is a ton of cash to only save 18lbs and not only that but the OEM battery tray is a big relatively heavy steel item as well.
Earlier this year I decided to optimize the weight reduction by re designing the tray and hold down. I wanted something that weighed less than an ounce, cost less than $2 and would be as strong as stock.
Naturally, I chose Velcro.
Before you LOL or ROFL, hear me out!
Its been several track days, a dozen AutoXs and 6000 highway miles and that thing is stuck in there for good. Im not joking when I say that I'm going to need a pick axe to get it out.
I removed the tray, cleaned the chassis with acetone and applied the fuzzy side. I did the same to the side of the battery with the hook side and just laid it in there.
I was concerned that the underhood temps would soften the glue or that the Velcro itself would pull apart. Nothing. That sucker is in there, I had to rent an engine hoist to pull it out! (not really, but it might come to that)
Anyway, if you run AGM batteries and want your lightweight battery mod to be as light as possible....
Velcro battery mount FTW!

 

call your battery MFG, most conventional lead acid battery will degrade rapidly if you let it vibrate, after a while the lead grid inside will how less and less charge and ultimately lead to premature failure.

i am not familiar with the type of battery cell you are running, call the MFG to make sure how much vibration you can throw at it without making it a paper weight.

 

Not as light as your set up, but I'm bolting down a ballistic nylon strap using the OEM holes to hold my PC680 in place.