As noted in a prior project log, I dropped half of the keyboard last week and the PCB standoffs failed. One cracked along a layer line and one had the adhesive fail. So with some suggestions from discord I've done another design of a larger mounting plate. The PCB will bolt to this with heat-set threaded inserts, and the mounting plate itself will then bolt to the wall of the slot box.
I'm going to try to make this work without printing another slot box, so I'll have to drill 2 holes in precisely the right locations and also try to countersink them enough so the bolt head sits flush. Since the walls are only like 2.4mm thick, this could be tricky, but it's worth a shot.