I would bypass the battery all together but that is just my opinion. However, If you want that plug back there/a way to run your compressor in the back... You would have to have the battery. I guess you could do a distribution block or have quick connections somehow but battery would probably be your best bet then I think. I would still have it tied into the alt- would be worthless dead haha

It would be like my sgt always said: would you go into battle without your weapon?!

(I was a contractor attached to a US Army detachment out if Ft.Bragg and in JROTC in high school)

I think I'm just going to run the lines up to the main battery. I havnt hooked up the OBA or 12V plug yet. It's bought and in the garage, just not connected. I'll figure out the duel battery with controller in the rear later when I have my current projects finished. Thanks for the replies and help!

Would this be the type of metal to use?

You're probably going to want something a little thicker, say 3/16 or 1/4. Check with a local steel supplier. They will have way better deals.