Went out to the garage and worked a bit more on the toe boards…  Decided to trial fit one of the firewall brackets to help me judge the best fit for the toe board patch:

Also started practicing some welding to fill in the holes in the toe boards before adding the patch panel.  The sheet metal going in is of the same gauge as what is in there, so I grabbed some scrap to play with and also used a copper backing as you will see:

Side that had copper plate backing: