Design update: to decrease labour requirements, I'm gonna be making a frame from 1.5" x 1.5" x 1/8" angle bar, and just bolting all the panels but the back one onto it. This will allow me to easily rotate or flip the motherboard simply by rearranging panels. The MB tray, rear panel, and frame will be all welded together, but aside from that all assembly will be bolts and screws.