Thanks Mex.
I do think I can make a thermal barrier.
I do wonder how hot it gets under there while underway. I've never thought to bust out the IR gun and check after driving.
I cut out the old battery tray and brushed some baking soda dissolved in water in the areas below the tray. They bubbled up nicely.
I cleaned the whole area well and applied some Ospho, and will paint it. Tomorrow
The Screwy 31 is now on the asphalt outside my Van. I have some alligator clamps on the end of a 45 amp anderson powerpole on 8awg cabling attached to the original battery cables. This might be the last cycle, but in theory I can just keep cycling it outside my Van.
The original battery tray is not quite salvageable. I'm going to design something that is easy to remove in the future.
There is some wiring to signal lighting, the and the wiper washer motor and the connectors are hard to reach with battery and tray in place. They were in pretty ugly condition.