Rich, this is really going to be something!
If you took 4 of these (Doubles) and had them as single units on the floor, left and right, can you attach those thicker flush tops to both sides, where they bolt together? It's a little tough to make out, but it looks like each modular unit has 2 holes on front / back of woofer sides where they are bolted together. Can you put 2 of those thicker, flush top caps on each one, so hey look the same? You mentioned earlier the different top cap versions and assume the caps can go on both side of the single modular unit.
What I may do is play with them with stand mount speakers, and have a modular unit on either side of the base of the speaker stand. I'd like them to look symmetrical rather than just a "disassembled unit of 2". If there are 4 holes in each, in addition to the flush caps, I could have some feet / spikes go all the way thru the "bottom cap" so I can have a nice setup of each of them being on the floor by themselves. Of course, if I need a hole... I can drill one.
Hopefully I'm making sense.