Hi AlaskaBill!!
Just joined to say thank you for sharing.
I have done some thing similar using 3d printer.
looking at your design, it will most suitable for the rifle cases, which Double Alfa is about to release..... using your upper (no sensing) and my type of lower.
I will try to modify mine to use your upper design.
I don't have tons of time, but I enjoy debugging and overcome problems by tinkering here there.
it took me 10mins to figure out your collar case release mechanism. not that you did not explain it, but I had to "see it" (like in X ray) how it works....
My design is posted in youtube
hopefully, it won't take me another 6 month to do the design modification... lol
Again, really glad to see an awesome work and design for RL550.
Thank you for sharing!!