Have you got pictures of that sill plate for the battery access cover?

 

I was looking at the LMC catalog and it didn't look like thier carpet does the complete floor under the seats, just 2 patches beside the them. I do like the provision to access the battery seeing as mine will be in the original location.

 

Watching this thread. Will be inthe market for a carpet for mine aswell. I've also got the battery in the stock location.

I know that over in the Mustang II Forums, they give Stock Interiors alot of praise for their product and service as well as price. Rumor has it that they are just a large distributor of ACC carpets. Difference being is that Stock interiors purposely orders all their carpets from ACC oversize (made with excess material) and with the better jute backing. So, no doubt, you're getting a qualite piece, either way.
If one were to order direct from ACC, they typically have pre-cut carpets they want to sell you but you can order from them 'oversize' as well at an extra cost. However, maybe ACC has a solution for the stock battery location?

 

I never saw the battery access as an issue since the carpet is easily lifted. Is it that some folks intend to glue the carpet in place? A simple piece of stainless angle metal placed along the upper edge of the rocker works great to hold the carpet in place and if you need to lift the carpet you can just pull it out from under the SS strip. Midfifty carries these strips as well...page 21 of the 2011-12 catalog, $32 a pair.

Here's a photo that shows another way to hold the edge of the carpet...notice the offset from the edge of the rocker, too much carpet next to the door will cause the edge of the door to push the carpet back.

 

Automotive Interiors - interior kits, carpet kits, seat covers

They also deal with only ACC and are good folks to deal with.

 

Would you have another picture showing the whole side. The carpet you are talking about would be in 2 pieces right. I'd like to see a picture of how it's layed.