Problem

This is the real problem. I don't want to use more than two LEDs per segment. Segments are somewhere from 25 to 29mm long. Using one LED is not enought to get an even glow. Using two creates a "dark spot" between them...

Solution

Lot's of testing had to be done! I ordered a few laser-cutted steel plates (2mm thick) to play with:

Number one and two (from the left) are spacer plates which I'll use to get some space between the light-source and the front plate. Plate number three is the front plate, where laser-cutted acrylic segments (opaque plexi) will be pressed in. Last one is the back-plate.