My current version has a sliding trigger, not hinging. It also utilizes a 1" thinwall priming insert, a different rainbow setup, and a tapered plunger rod that sits outside of the catch in the unprimed/resting position. The sliding trigger is smoother and allows for very consistent slam-firing.
A big reason why I abandoned your type of design was to optimize part fabrication and cost efficiency. Every plate on my current version can be built out of sheets measuring 12"x12" or less, eliminating the cost of 12"x24" sheets (and shipping costs less too.) Plus, all of my templates require no overlapping when applying them to the materials. If you've had the misfortune of 2 plates not lining up due to maligned adhesive label paper, you'll know that overlapping templates is a pain in the ass.
I hadn't seen Drev's design; I guess there are only so many things to do with a backward facing plunger and a foregrip.
Earlier on in planning, it had occurred to me that using a sliding trigger lets the whole thing be shorter, after which I realized I was happy enough with this, even though it isn't ideal. As a side note, this is essentially as short as you can get with a pivoting trigger.
Using the thinwall 1" pipe would have been a great idea, if for no other reason than making the catch easier to make, what with more space for it to fit into.
And it did seem to me at one point or another that using 12×12 sheets (and good on you for doing so) goes along much better with a sliding trigger - it keeps functional parts more towards the back and thus needs shorter side plates.
As to slamfire - kinda... When the 1" slide is in the primed position, the trigger pops up into the 1.25" pipe too much. That could've been prevented by extending the 1" pipe towards the front a little more.