The original project was going to be all acrylic.  There would be multiple layers.  The backing would have small 5mm square holes for the neopixel to shine through an illuminate the dome. I had planned for the bottom layer  to be one large piece that would support all other pieces.  The second layer would be a single hexagon with a two inch hole cut out of the center.  The dome would then be inserted into this piece.   The top most piece of acrylic was a border piece.

So the dome I was using was just a plastic ball cut in half, and not really what I intended to use,  so I thought I would vacuform the domes.  This did not go well.  I had read a few blogs, but there were nuances I wasn't aware of. That and I melted the ball.  So I ordered a acrylic half sphere.

I'm a member of the FamiLAB hackerspace,  I guess we have experts on everything because Mike and Pat  helped me get setup and running.  Pat was working on eyeballs for Starbots so this was very similar to what he was doing.

I cut it out and held the dome in place over a neopixel and was impressed with how the light glows (picture doesn't do it justice)

At this point I was happy with the project, but I didn't have enough styrene to make all the domes, so I experimented with my last piece and... it looked good.  I tossed the original design at this point. One point that always bugged me was the acrylic being shiny and the dome wasn't.  If the lights were not on it wouldn't look uniform.  This changed everything. The experiment had a better look and feel than the original.

So I made a few measurements and  cut out a back plate (hex), standoff, and a ring to prevent the light from shining beyond the dome.  The ring also supports the styrene just around the dome.