I'd want to show you our variant of Niewiadow's repair. It is currently in progress, so new images will be added.
Special thanks to your site for main ideas, and again sorry for English here

We got N126 produced in 1988.

Previous owner tried to repair the internals, but made it too unsuccessfully. Bamboo walls were mounted on wooden bars 3x4cm, which are glued to 3cm styrofoam. So internal area was reduced by 6cm from each side (!!!)


We decided to unmount this terrific construction,

as well as flooring (8mm OSB was corrupted and seemed too weak)


Using the experience of people here we covered corners and risky non-waterproof surfaces with "liquid-plastic" paint


Then enforced the floor with unmounted bars 3x4 (glued it perfectly with Poland-made Dragon)

Covered it with the 8mm polypropylene hydroisolation:

Cut the floor from 22mm OSB plate, and finally mounted it on
its place:


While I was screwing the floor,

my wife glued the depths in the walls with 1cm foam rubber (to lay the future carpeting smoother)

like that (used "liquid nails")

To relax and add our work aesthetic part we refined our wheels:
cleared

bought spray primer and silver paint

painted


After that the entire wagon (except roof) was thermo-isolated with 1cm foam rubber (glued on the same liquid nails)



Then the most funny moment has come: we choosed the carpeting and mounted it in our wagon (used rubber-based montage glue Tytan RB-22):



We stole the idea of ceiling made of PVC panels here



Because we hurried up to meet my wife's birthday in our first Niewiadow trip, we threw away hard work and made some decorations and comfort thigs like toilet shade and curtains. Yana sewed it perfectly:


After 1000 km of test trip our construction showed high reliability. Nothing had fallen off. Glues and other attachments are good.
Then we continued N126's repair with hatch repair. The same 1 cm foam-rubber has been glued

I replaced all the screws and washers with new ones with rubber layer (they all were rusty, rain water flawed throw them, and some of them I had to nag)



After mounting back it looked like this:

Next mission was to replace the died rubber sealant to a new one and cover the PVC edges with plastic corner.

the original sealant was unreal to find so we glued a cutted furniture sealant

The floor was covered with 4mm hydroisolation to make it warmer and finally hide roughnesses and screws hats

And then 2.5 mm linoleum has been placed on.

At the moment we are projecting the furniture and energy sources, so to be continued...
