Nicely done insulation (post #4)! Can't wait to hear how that works out, since you're in hot country, which is the kind of temperatures where I have the most trouble--a sunny day in the summer in Utah is a challenge.
By the way, I take the simple approach to electrics. I use a small 4-breaker box from HD (like $20) for 110V, with one breaker as the mains, which is GFCI, then one for the A/C and the other two for two general circuits. For 12V
, I use an 8-position automotive fuze panel ($17) that can handle 40 amps and I fuze for that. (the advantage of this setup is that the fuzes are easy to pull and a fuze can act as a battery switch--if it's in a handy location you can pull it and guarantee that the battery won't get run down.) These fuze blocks have two rows, so I put the batteries, converter, and tow vehicle charge line on one side and the 4 12V
trailer circuits on the other. I don't use an inverter, so my biggest 12V
load is the water pump at about 7 amps. Lots of members are under the false impression that they have to use starter wire size cables for the batteries. Last time I looked, I don't have a starter motor in any of my trailers
. Even #8 wire is mostly overkill--you'll never have those kinds of currents except for the first few seconds of recharging a completely dead battery. At that point the 40 amp fuzes let you know you've got a problem. Even my tow vehicle (F-250) is factory fuzed to deliver only 25 amps of charging current, which sort of sets the standard, IMHO.
The only benefit of a converter bigger than 45 amps is that it would provide a faster recharge on the batteries. If you're really a boondocker and operate a fair amount of time off your battery(ies), your max draw will be around 10-12 amps. Even a "big" automotive-style marine battery will only have a capacity of 115 amp-hrs, and you can only use 80% of that without damaging the battery. So if you want to boondock for 4-5 days, you have to plan your 12V use to average 5 amps or so for about 4 hours a day. One of the old vent light fixtures, with 6 bulbs, was a real battery killer all by itself!