John giveth and John taketh away
If we remember: 
The interior of the gun body has no place to mount a enclosing panel (and whatever else) to the bottom. This cannot stand. So, I got my trusty Bondo out, used a few pieces of thin plastic taped together to form a crude mold, and set about creating pegs that I could drill holes in, and eventually screw the bottom panel into. The results are thus:
You can see at least one corner is horrible irregular and the outside no longer has silver paint everywhere. The pegs, overall, are probably much larger than necessary, as well. Looking at the next pictures:
You can see this more clearly. Where each "peg" of Bondo is, I drilled a hole through the plastic so the Bondo could fill through this hole and better lock into place. In fact, the hole gets wider toward the outside of the gun body. So, assuming the Bondo doesn't "break", it cannot separate from the wall of body because the segment in contact with the outside is larger than the hole near the inside. Of course, it's pretty thick stuff so I couldn't just pour it into those holes. I had to allow extra Bondo to dry on the outside, then sand it back down. Hence the mess you now see. Next time, I'll shape the pegs, themselves. I figure it would be safest if they tapered toward the wall as you go deeper into the gun body. Less chance of me hooking one as I'm working inside there, plus it makes room for the many, many things that need to reside in there.
The interior of the gun body has no place to mount a enclosing panel (and whatever else) to the bottom. This cannot stand. So, I got my trusty Bondo out, used a few pieces of thin plastic taped together to form a crude mold, and set about creating pegs that I could drill holes in, and eventually screw the bottom panel into. The results are thus:
You can see at least one corner is horrible irregular and the outside no longer has silver paint everywhere. The pegs, overall, are probably much larger than necessary, as well. Looking at the next pictures:
You can see this more clearly. Where each "peg" of Bondo is, I drilled a hole through the plastic so the Bondo could fill through this hole and better lock into place. In fact, the hole gets wider toward the outside of the gun body. So, assuming the Bondo doesn't "break", it cannot separate from the wall of body because the segment in contact with the outside is larger than the hole near the inside. Of course, it's pretty thick stuff so I couldn't just pour it into those holes. I had to allow extra Bondo to dry on the outside, then sand it back down. Hence the mess you now see. Next time, I'll shape the pegs, themselves. I figure it would be safest if they tapered toward the wall as you go deeper into the gun body. Less chance of me hooking one as I'm working inside there, plus it makes room for the many, many things that need to reside in there.