Here's a quick pic of something I was working on early last month, which, for the sake of this post, I'll call Project D.
It's a customer project and not my design, but I made every piece shown (plus the ones inside) except, of course, for the two hose nipples and the Freak barrel.
Stacked tube, not striker-fired, typical quick-release bolt like a 'Timmy or Ego, and internal air lines like a Mini (the adapter block on the grip frame is just for bench testing.)
Despite some... issues with the supplied drawings (like a part 0.406" tall that's somehow supposed to fit in an area of the grip frame that's only 0.3125" thick* ) it was a fun project. Looking forward to seeing it polished up, annoed and assembled.
*Yes, I made it fit. I had to bend space and time to do it, which almost collapsed my shop into a singularity, but hey. That's just the kind of airsmith I am.