In order to fill out the main part of the proton pack, we ordered pre-made vacuum-formed plastic shells. Here, I have done some highlight work with silver paint, in an attempt to make the black plastic look like weathered metal. I have also mounted the shell pieces to a backing board cut from MDF and painted black.
Here, the shell and back plate have been mounted to a military surplus ALICE pack frame picked up on eBay. Authentic AND cheap. At this stage, most of the mechanical construction is complete. Now, all that remains to be built is the gun.