The LED strips without massive spaces around the LEDs are a good find and might work. So your saying that with sideglow, the LEDs usually face down? Because if so I can remove the extra space I made around the PCB.
yes, always facing down
you can use any acrylic, just give it a good light sanding (including edges) and you have "frosted".
- space them in closer to the center of the board for a more even look, get too close to the edge and you really get differences in brightness and can easily pick out where the leds are located.
look at the image you posted. it's not really apparent in the edge, but if you look at the reflection, you can see what i'm talking about.
do a google search for "pcb underglow" and look at the images for examples of how it's typically done.