Added a battery disconnect and voltage display.
The CO2 detector and possibly other items drain the battery in spite of the shut-off under the sink. I'll call this an "undocumented feature."
The battery disconnect was installed on the battery box top/side and connected to the negative using a gable extension. The display just mounted to the top.
Qiorange Car Battery Isolator Disconnect Cut OFF Power Kill Switch
Camco 47473 Black 5/16" Stud 12" Long 2-Gauge Marine Battery Cable and Lug Assembly Tinned
Mictuning DC 12V LED Digital Display Voltmeter Waterproof
You'll need a crimp connector set and the larger round attachments to attach devices to the leads. Use waterproof silicone sealant when installing. On this one I drilled a hole for the key slot then ones for the screw mounts, mounting from the inside. I mounted it with the leads on the inside horizontally so it would not hit the battery.
Also, the Solar Panel connector is just a standard 2 pole connector, but has reversed polarity compared to some charges with interchangeable accessories. Just get a 2 pole connector set and cut/crimp the wires to cross over connections.
Test everything with a battery tester! On the disconnect you'll want to turn to the "on" position while towing for the backup brakes and for charging.
Also installed a roof basket without breaking the bank.
Many of the less expensive racks are not quite long enough to reach the fixed cross bars by about 2" . I was able to find this setup online for less that $100 and seems sturdy enough considering you are only putting about 100# max in it. The Reese (and their clones) will not work, it is not long enough.
TMS ALUM-RFCARRIER-CH41 Cargo Luggage Rack
I attached using lag bolts slid into the slots on the cross bars and clamped using pre-drilled strap/sheet metal, using my bench vise to bend the ends down. I'll probably paint later. Used acorn caps to top off the tops of the bolts.
Although some have stated there weren't instructions with this rack, there were in mine and took under an hour to assemble with a power screwdriver.
Clip on Fans and 12v plug
Next up will be modding a auto clip on fan to use the roof 12v power connections by the beds. Also installing inside/outside 12v accessory plugs (standard and BMW style). I have not tested these yet, but it worked with the same connection for the backup camera setup.