I'll just let the photos tell the story. Didn't use foam padding, just flexible leatherette from the local sewing supplies store. Dipped into my store of aircraft upholstery supplies for the cement, which is a high-solids, high-tack cement used to finish aircraft interior panels. Seam was tightly sewn to the edge as close as possible then trimmed carefully.
Key is to let the cement flash off completely, and use a sharp razor knife to point the leatherette as you go around curves or inside corners. It's fiddly (no doubt the ladies in the trim shop at Hethel were a lot faster), but if you take your time, it all works out well enough.
Fiberglass base was stripped of all the old cover (which I used as a general pattern...), foam, then sanded lightly to remove the old cement. Luckily it was in good shape and ready to receive the cement. I did one panel at a time, starting with the front, and stretched the leatherette as it was smoothed down on the base after the cement flashed off.
Think it came out OK; it only has one attachment screw in the front face that goes into the switch mechanism metal flange. Thinking, for sturdiness sake (and to give the switch gear a little more stability), I may put two holes in the bottom that align with the base of the dash, and use some #6 black trim screws up from the bottom, and build a short flange out of aluminum and do the same for the top. We'll see when I get back to MA and keep working on the car...
