Thanks westend, please do not jump through any hoops for me.
Yeah, I'm guilty of overfilling. I tried the mirror and flashlight method to estimate electrolyte level on the 3 difficult to access cells, and missed the mark.
I have two friends who are practically hoarders and will see if i can find something i can cut to size which already has two lipped sides. I do have access to a welder though my welding skills are lacking.
The thermal barrier between battery and engine compartment is going to be more like a stiff shiny roll up blanket, or a least something easily detachable.