So I ordered some clamshell rings to get away from the 3-point ring setup, and risk of flexure. They say 'TMB' on them and they're real high-quality, so I guess Astro-Tech acquired them in bulk from TMB at some point.
Here's the triplet mounted in the clamshells, with a 7" ADM vixen dovetail screwed in atop the clamshells. Then, two small dovetails clamp to that rail, and they each have the 3-point ADM rings attached. Since the guidescope weighs nearly nothing, I'm not worried as much about flexure with that. With the Parsec, the filter wheel, and the heavy MoonLite on the triplet, I needed rigidity down below.
Lastly, the Losmandy plate the clamshells will attach to arrives tomorrow, hopefully the space between the holes sets up right.