No pictures, but I extracted the cheesed VESA mount screw using a flathead that happened to be exactly the right diameter; that was lucky. I replaced it with the wider spacer. I then tightened the socket-head screws down more and discovered what the actual problem with the thing was: one of the threads in the monitor itself is FUBAR. I spent a lot of time measuring and looking and considering how to handle all of this.
I decided the design was misjudged in the way it worked; there are about 3" of assembly between the 8020 vertical the monitor is attached to and actual monitor. In essence, a lever on a fulcrum, and some of that is there because of a perceived need for an 'easy to adjust' monitor height mechanism. Once I set the height months and months ago, I haven't adjusted it at all. So I'm replacing the ratcheting handles with hex-head bolts, which will, of course, with the limited space, require a standard open-ended wrench to adjust, but given how infrequently that would be done, fine. I ordered a number of different sized spacers and bolts from M-C, and another aluminium 1x4" drilled plate from T-Nutz.
I'm going to be doing some experimentation, but the intention is to remove as much of that length as possible. The amount of force on the monitor should go down massively for every fraction of an inch I can remove and still have it work. If I'm really lucky, I might be able to eliminate the intermediate plate entirely.
I got the new monitor, and tested it to make sure it works (I've had a DOA before) but I'm not going to install that until I finish redesigning this assembly.