Thats a good set-up.....but I still think you should ditch the cap, and upgrade the main battery to an Optima, or Kinetik. I also think u should ditch the box, and have one built to spec for the L7 thats what I did for mine and it makes the world of difference, thanks to a buddy of mine. So order everything, but the box and the cap.
Good Luck - Post Pics of installations - late