I think I said before that I was worried about the piston shifting around while shooting. I fixed this problem by drilling/tapping a small hole in the back of the grip here.
The set screw going in at that location pushes the piston up and to the right slightly, wedging it against the MAC valve (which is held in by two screws itself), so I'm 100% sure the piston isn't going anywhere now.
I also had to custom build a safety for this thing. Wish I had taken more pictures of that process.
I might still have to fiddle with the Level 10. (It didn't reset once during a test firing.) But otherwise this beast is done.
(I really need to get better at walking the trigger one of these days....