Here are a few observations. I watched the Redpants video - thank you for your efforts. I came across a couple of things that were different on my 2011 V8V S roadster.

I bought a mini ratchet and bit set, Sunex Tools #9726 from Summit Racing for about $23. Very small and made the tight spots easier to work in.

My hold down strap used two different sized torque head screws instead of the #10mm bolts. After removing the strap, I used the mini ratchet with the T-27 bit to loosen the four screws that hold the two sliding brackets down. I then slid them towards the passenger door and was blocked by the carpeting. I wrestled with the carpet to no avail. Quit for the night.

The next day, I looked at the brackets from different angles and decided to trim the fiber channel that is connected to the carpet. It only took a small cut with a razor knife (box cutter) and the brackets slide right off.

In this photo, I have the bracket slid to the left to show where I trimmed. The next time that the battery needs replacing,
the vertical carpet can be pulled towards the seat back, and the brackets can be slid right off.

The lower pic shows the tool kit in a nice case. Will come in handy in the future.

Thanks to everyone who offered advice!

 

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well done and thanks for posting

 

My first post here having just got my V8 Vantage. The battery ended up needing replacing very soon after I bought it, I found the redpants guide invaluble but one interesting difference I found was that instead of sliding the brackets off - I was able to back the bolts/screws right off and then there was enough play in the clamp to wiggle the battery out without fully removing the clamps. Careful alignment of the new battery let it go in in the same way. Thought that might be helpful to someone.

My arms are killing me - those batteries are seriously heavy!