Why not giving it a little bit of colour?
At the moment we have 22 Lights each wagon on the U1. Opening is quick and easy with a srewdriver via 3 screws. Sizes are 120 × 17,5 cm.
Depending on the amount of discos you wanna do you have to buy the coloured sheet.
I recommend www.modulor.de or www.caststore.de
Make sure to compare the prices in coordination with the size of your project.
Let me know if you did it and send me some pictures.
I propose these coloures: