Jeff,
I recommended the Ergotron triple monitor mount a while back on on of your posts about the triple monitor club.
I really like the model I have and I’m curious why Steve waved you away from it? It has all the same feature you list here for the 2x1 and the 1x1 and has the added benefit of being just a bit less expensive (well, $170 less expensive).
Why, Steve, Why?
One benefit I see to your setup is that it completely opens the space under the monitors.