May I ask, "What did you decide on door cards?"
As a background, I am expecting body parts back in from the paint shop starting this week. So the final ( .... maybe) phases of final build and titling the vehicle are in front of me. And as usual there are a few build items I have not started yet, such as bonnet skate wheel rollers and ... door cards. I am likely to cloth these cards in the same leather I upholstered the dash with. I wish to make them easily removable so that I can remove the BRE side mirrors as may be needed from time-to-time. So 4x rivnuts are likely in the plan for each card. I have not decided on the door card substrate. I have some sheet aluminum, which is a candidate, but am considering using some ~1/8" ply (I have some baltic birch lying around from some RV interior work last year).
I am hoping your battery woes have been resolved??
... Bob