When I have finished my boxes, I have decided to try to put it all together. Because I could not tested it if it works without this display case.
I have made a mistake in calculating all the sides and the room I needed for the perspex, so when I tried to put it all together only two sides of perspex fitted.
So because of my lack of mathematic abilities, I needed to sand off 10mm of 6mm MDF. It took a lot of time to sand all the boxes, but at the end it worked perfectly and I was able to fit everything in.