Had a chance to put in a little more time on this project.
Here is a shot of how the tab will sit.
Using the wood template, I laid out the tabs and marked and drilled 5/16" holes. Then not being confident of my measurements, I decided to steal from the Porsche engineers. I drilled out the spot welds to reuse the left side "nuts" and carriers.
I used one to mark the metal I needed to remove to expand the hole.
Made the hole bigger and welded the carrier with "nut" on the tab.
That should make mounting the seats a tad easier.