I got the hardware for the packs. So, I printed another test. The previous plates were designed for a smaller threaded rod, but this 6-32 was actually a good amount cheaper than the 4-40 rod I had designed it for.
So, new plates were printed up. I assembled things and it went together quite well. Once the threaded rods are in place the assembly is very sturdy.
I am seeing that it'll be difficult to print such a large flat plate on the 3d printer. When you print these pieces, they're warm plastic. As the print continues the plastic cools off which makes it shrink. This shrinking ends up making the print potato chip and peel itself off the table. It'll be interesting to try to get this to print correctly. The test plates came out okay, but did start peeling up which distorted things a little.