Thought I should circle back with a build update. Thanks to the long weekend I got 3 days of mostly trailer work and much less child wrangling since my wife was home.
Last weeks I was able to get the ceiling installed and lights up. In hind sight I wish I would have put some sort of furring strip up where the seems would land. It looks like crap as is and will need to be trimmed out with either more luan or some 1x2.
You can see I've left a 4" wide channel exposed to run all my wiring. I'll trim this out where it's not covered my cabinets. It will let me go back and make electrical changes without having to strip everything down.
The walls went back up pretty easily. I took advantage of them being horizontal and put a coat of primer on them so much cleaner that painting in place.
I am so happy that I paid extra for screws instead of the hell nails. Best $100 I could have spent.
I bit the bullet on Sunday and cut a big ass hole in my trailer. I was a bit nerve wracking, but nothing to tricky. I did learn that my build tolerances are much tighter than the typical RV/trailer shop. I had a hell of time getting things in place because the hole was only 1/16" bigger than the window. I think I'm going to struggle with the next window and the frame has less slop than this one. I did the cutting with a jig saw as is suggested and it worked well. I'm so happy to have an oscillating saw as it worked really well to cut back the plywood for the trim ring. It's like cutting plywood with a really loud Exacto knife. 30x22 exit window.
Here's a handy and cheap tool I've found invaluable while working on the trailer. I got some strong neodymium magnets to mount my backup camera monitor in my truck and found they make really good 3rd hand tools while the wall are off. cuts some scrap 1x2 and 2x2 and screwed the magnets too them. I used them to camp furring strips to the trusses before screwing in. The helped hold the plywood in place while marking things up. They can hold wires out of the way. They can hold window templates on the outside so you can draw a cut line. They can find framing from the outside. Handy in all sorts of handy uses.
https://www.amazon.com/dp/B07YSTJ4TR/re ... aFbY1GGNC7 
Lastly I had on sizable oops this weekend. I was cutting out a hole for my fill dish and "found" a double stud that didn't have any screws in it
. I measured twice but did not double check with the above magnet to make sure it was clear before I started cutting. Thankfully I was checking progress and didn't cut the stud. I've ordered some .025" diamond plate to trim out my "water services". It will make it much easier to clean up spills than scrubbing on the paint.
I'm glad this was the screw up for the day and not too big of a hole for the window. That would have sucked.
I moved my hole location over a couple inches to clear the stud and ended up cutting my wires for the water pump.
I was really pissed at that point! I had to pull the lower wall panel off and solder/heat shrink the wire back together. I didn't have any more long runs to redo it less than ideal but should work just fine.
I spent some time today wring in the relays that will control the ramp/backup lights and running lights from the interior switch panel. The running lights will come on with the porch light so you can find the trailer while stumbling around in the dark. Here's how I did it.
The N/C connection is always connected unless both interior switch and master power are on. Once the switch connects the relay coil to ground the relay changes the power source to the house battery.
Much easier to undo later if need be.
