I've managed to drill the holes in the CP and check that everything lines up. I need to trim a couple of mm off the side panels and then I can glue and screw them into place before sanding it down and filling it.
Dry assembled:
Back:
You can see the chamfered sections to act as guides to make slotting this in as easy as possible. The middle chamfered piece has a threaded insert to allow the panel to be attached to the base section.
I've left about 1mm around the perimeter of the acrylic to allow for the layers of paint.
Edit: trimmed, and glued.