Sorry for taking long, my own group-buy require more work than I expect... buried in excel sheets all day.
Just did the acrylic test today. Unfortunately the acrylic mid-piece was failed when I cut it and I'm out of thick acrylic stock. Will try again tomorrow, when it done I will move to CF final product. I will try two slimmer acrylic piece 5mm instead one 10mm thick - thick acrylic led to less precise laser cut at the back.
But the top and bottom pieces border shrinking was okay, should not have any problem by now.
Spacing for largest 60pcb (same size of 60% plate) - okay
USB port having one more hex post, should be enough to keep the acrylic mid-piece in place - total 9 hex post.
There's lots of room under the pcb, should I shorten it so the case look slimmer?
Hopefully everything will be set in motion this week
UPDATE: this is how the acrylic mid-piece will rest. I'm out of thick one so this is a test on slimmer 5mm acrylic. It will be flush with the hexagon post with right thickness.