Three windows in the van

I got six 50 cm x 50 cm tinted acrylic glass plates from here: 

https://www.plattenzuschnitt24.de/Acrylglas--getoent-Schwarz-3mm.html

The location of the windows: on the left side.

The wall before any modifications

First modification: cut through the wooden bar where the windows will be.

Placing the window plates at the location where they will later be.

First I created a template for the windows cutout with cardboard. The corner roundings I designed from the tape roll radius.

Then I attached the template inside at the location of the windows and drew the outline. Hereby I could adjust the location so that the windows are approximately equally spaced apart. The vertical beam structure of the Luton box is here not very helpful - all of the segments have a different size.

Template affixed inside.

Then I did drill 4 pilot holes to indicate the location of the window cutout. From the outside I then drew again the template over all the pilot holed from all the three openings. Then I used the electric jigsaw and gut the openings.

Here they are:

Next I affixed the rubber seal around the edges.

And finally I attached the acrylic plates from the inside. Here is how it looks after they are in place:

First I did screw the plate onto a horizontal wooden bar, which is latched against the vertical metal structure.

Then I rotated the plate upwards, and attached more wooden bars, pressing the plate from the inside against the rubber seal.

One can easily drill new holes into the plates. I had a few pre-fabricated holes, because I was not sure if the plates would survive the drilling into them with my drill, but it worked great.

And this is how the three windows look from the inside in their final state:

I also began to add some insulation at the wall. Needs to be completed, then I can begin to add the final panels.

Here are the windows from the outside: