Hear ye hear ye,
On the 1st day of the 6th month in the year of our lord 2022 The build has begun.
I've been designing off the specs EZ posted on the NT trailer, which are spot on, Thanks EZ.
Today I put the frame box together so I could lay out the new location of the axle and frame cross bars as I am extending it by 2'. It's sitting at 20 3/4" off the floor on the jack stands, which is 3/4" high per EZ's specs.
I'm going 65/35 on the axle location, the trailer uses 2 C channel cross bars at the axle, I'm replacing those with 1 pieces of the 3" 1/4 wall channel iron I scored at work. Once I get it all bolted up I'm going to break out the welder and go at it then pull all the bolts. Despite NT includes nylock nuts, I'll feel better not thinking about a bolt working loose in the future, besides it'll just make the frame all the more rigid.
I also scored, from work, an old 2"x3"x 84" table saw fence guide rail to use as a rear bumper and seeing I now have an extra cross bar from the OE axle location, I will use that to extend the side frame rails to 10' and hang my bumper off of those.
Also mocked up the spare tire location. I plan(ed) to use a GM spare tire cable hoist but I don't have the top clearance, but if I relocate the hoist back behind the front frame rail, mount it horizontal and use a pulley to get the cable where I want it, I think it'll still work, this will leave 12" clearance from tire to the ground. There will be a triangular tongue box taking up most of the tongue, the propane tank, diesel heater and 160W solar panels will go in there plus some extra storage. I'm still undecided about putting in some 6-8" deep in floor storage bins in the first frame bay. I could cut those in easy enough at a later date if I choose, I'll at least plan for that in my floor framing. My concern is the camper will overhang the side rails by 8" on either side so cutting out structural framing might leave me a weak spot at the door.
The Sketchup drawing also shows my fresh/gray water tank (16/10 gal) locations. I placed the fresh water tank on the right side as my mechanical closet is at the left rear corner where I'll have the battery, on demand W/H, Inverter, converter, power management etc. this should pretty well balance those two locations out.
It's a bit tight in my garage but about 4' of the width is being taken up by my scavenged materials.

As far as NT's build instructions go, they pretty much suck just like everyone says. I laid everything out oriented per the picture, those holes go on the bottom, those holes go up front... When I went to attach the tongue bars, yeah the cross bar was upside down, and would it be to much to ask to put the 16 1.25" bolts in a different bag than the roughly 40 1" bolts and nuts.