Hi, stomperxj:
Your build really shows your knowledge and skills. You're doing a beautiful job!

If only we all were as capable as you!
As I was looking at your battery box and the underside of the deck, I noticed that the trailer appears to not have a water shield to protect all your hard work. Obviously, you are building this extra tough so it can handle rugged terrain and you will probably be fording some streams and occasionally will be in rain and/or snow; so, you probably have a plan that just isn't evident yet. (Please forgive me if I missed something in the 8 pages of build pictures and notations.)
What is your plan for the subflooring water shield? Are you going to lift the body above the metal chassis so you can get at the underside of all the deck plywood? Are you going to apply roof emulsion or you do you plan to use the Kilz listed in your spreadsheet or.....?
OOPS!

Scratch the above. I went back and found the picture where you coated the floor; but, I don't understand why that black coating doesn't show in the pictures of the underside of the installed battery box. Isn't that built into the deck floor?