Today I finished off the dual battery setup I've been wanting since we bought the trailer. I bought a piece of 1/4" aluminum treadplate and some 1 1/2" aluminum angle material. Since I don't have a welder, this was assembled with self tapping countersinking screws. Thanks to suggestions from this forum, I found the starter wires in various lengths at Kragen and CW provided the second battery box & cut off switch. With this mod, all LED lights and some battery (D cell) operated fans, we should be able to run the DW's CPAP and everything else we need for a weekend with a little juice to spare.
Thanks to all for suggestions and answers to my questions!
Moderator edit to re-size pictures to forum limit of 640x480px maximum.