I installed new Barksdale Height Control Valve on each side with dump that I bought on Ebay for $45.00
A manual valve turns the air supply off to the HCV then a momentary switch activates a solenoid valve to supply air to the dump side of both HCV. Takes about 10 seconds to dump the air bags on...
Check what an inverter draws on standby.
I've had inverters that draw 4 amps (96Ah / 24hour) on standby.
I went with Victron because it was one stop shopping but I use Xantrex and ProMariner for backup
Yes, fumes will damage electronics. I've seen many metal battery compartment corroded due to acid vapor. Even item that are 5'-10' away affected buy the acid vapor.
AGM batteries might suit this application the best
Many years ago I went through the process. Bought a used tank , mounted it, a station refused to fill it because of rust, took the tank out to paint but a wire wheel wouldn't remove the rust so I called some propane shops to find out what they do. One place offered to look at the tank for free...
You've received decades of knowledge/wisdom from good people.
My $0.0002 would be to choose the battery type and number of Ah (amp hours) leaving room for expansion then choose a charger that suits the battery manufacturer's charging specs.
FYI......I have a bank of Crown batteries. Crown...
Thought I'd mention the angle around the panel is designed for horizantal mouting. Hanging may cuase the angle to roll/twist with 44lbs bouncing on the back of the trailer. Might sit the bottom edge on/in an EPDM lines tray.
A little slope will help the rain/dew run off.
I didn't bother installing any protection for the portable panels but I did put fuses and a disconnect on the roof panels because I didn't want any live wires in the trailer when it is in storage.
Tire rack and roof rack would be similar to the pipe/tube /plate used to build yachts but boxes/sheet metal is another can of worms. Laser will provice the cleanest edge for welding stainless. Router is best for aluminum.
If you've seen his sheet metal work and are happy with it then you're...