The motherboard tray was too large, so I measured things out and then used a Dremel to cut off the excess bit. Clamping down a piece of flat aluminum angle protects the surface and makes the cutting easier by allowing the cutting disk to butt against it, which keeps the edge cleaner and straighter.
I needed to find the proper location for the motherboard and window, once that was figured out I taped down the window template.
Below shows placement of the motherboard tray, having hardware in hand let me know that there are a few aspects of the mirror illusion design I still need to work out. They are small details and I will figure it out, but until then there is still work to be done on the back box.
The SMD LED strips that I bought for the sides of the back box were just a bit too long, luckily they can be cut at every third LED (as shown below), so crisis averted.
I installed two SMD LED strips onto the left and right side pieces of aluminum angle, I also rivet on support pieces for the 23" LCD monitor and cut 3 1/2" out of the bottoms of the angle to make room for the speakers.
Below is the 23" LCD monitor test fit onto the side support braces, since this monitor isn't VESA mountable it will be held in place with 3M heavy duty mounting tape.
It will also be held in place by an aluminum angle support brace on the bottom, the brace sits just beneath the edge mounted monitor control buttons, so they are all still fully accessible.
The 16" LCD monitor is VESA compatible, but I almost wish it weren't because 3M mounting tape would have been a lot easier than the home brewed VESA rigging I built for it.
This next picture shows how my Franken-VESA mount attaches to the back box, the four LCD attachment points are actually recycled bits from the 40" HDTV I tore down earlier.
Both monitors are shown test mounted below, since the front of the back box has a tapered edge the important and difficult thing is keeping everything lined up straight and even to the front edge.
To mount the speakers I cut a piece of aluminum angle slightly smaller than the height of the speaker and then cut a piece of 1/4" acrylic the same length as the alum-angle but slightly wider than the speaker and used two screws to hold it together, it is mounted onto the back box side aluminum angle with four rivets.
I will either use 3M mounting tape or Weld-on 16 to attach the speakers to the acrylic mounts I made. By cutting the bases off of the speakers I can get more left/right, up/down movement to better center them, unmodified the speakers sit tight to the 16" LCD monitor and level to the front edge as shown below.