Now, I've been using this for a while and have a few callouts to anyone who is thinking about designing a similar one.
1. If you're going to build a 4-player cab like mine, then 1 big mistake I made is with how the display is inset. This is more of a 3-player build now even though it supports 4 players. If you look closely, the display is about 4 inches into the cabinet. The IR LEDs then surround the screen. Well, the lightguns can only see all 4 IR LEDS if relatively in front of the screen. The ~4-inch inset of the display causes the sides to act like flaps that block the IR. So if you are too far off to the side, then only 3 sensors will be visible. Only 3 people can visibly stand in front of the screen and see all 4 LEDs.
I should have cut the sides in more so that they're flush with the edge of the screen.
2. soldering the gx16 was pretty tight since it needed to accommodate wire that was thick enough to handle 24v at ~3amps. Between the sockets, cables, and lightgun, it means that you're going to be soldering 16 tiny ends that barely fit into the casings, and then make sure that there are no shorts. I'd still do it again because I think it's worth it, but it's probably the most tedious part of the build. I'm looking to limit mine to 2 people only, but that's still something for me to consider If I ever wanted to add additional guns it's definitely something I should plan for on the front end of things.
3. I got the Streamdeck partially because I thought that I could use it for keyboard events as well. I.e., have all of the Dreamcast buttons available to navigate game menus and whatnot. Unfortunately, the thing does not support raw keyboard events. It sends system events. This means that emulators which rely on raw input (such as Flycast) cannot use the Streamdeck to send keys because it either support SDL or raw input, but not both. Emulators that support SDL are ok though.
Not too much, but I mostly wanted to call out #1 since it's a pretty important defect.
FINALLY, I've attached my sketchup plans to the original post in case anyone wants to use them as a base.
Thank you for taking the time to share and be so detailed with how your process went. I imagine I'm far from the only person who has been considering such a similar build and your sketchup file really breaks it down ( I had started doing something similar with graph paper and you just saved me probably weeks of time!) Additionally, I was curious about how the stream deck fit into your overall build. Finally, just want to say the finished product is truly a piece of art