The psu went kaboom while I was installing the OS, so I had to order a new one. Luckily everything else is intact, the new psu has arrived since then and the computer is working again.
The monitor.To place the monitor perfectly under the bezel board, I put the bezel board on top of it, adjusted it until it fit and doubletaped battens to each monitor side from underneath. Then I flipped the bezel board upside down and put the monitor in. To hold it in place, I glued two sets of 3 battens together, glued those to the bezel board and screwed a piece of scrap wood onto them. Then I screwed the monitor to the scrap wood.
The bezel board is 50 cm wide, the screen only uses 30 cm, so that left 10 cm space on each side. Too much. I took two strips of wood, 4cm wide with a rounded edge on one side, stained them, waited 8 days for the stain to cure, clearcoated them, waited 3 days for that to cure and doubletaped them onto the bezel board.
This is how the monitor will go into the cab, there will be no plexi or glass cover. The screen has an anti-reflective coating, I don't want to negate that by putting something reflective over it.