Thanks Tel. I made a mistake in my reducer spreadsheet somewhere...calcs for TFOV came out larger at 20/24mm than the optical back should support...what got me wondering about the real-world results.

It sounds like a few people have done this with the Hyperion zoom (further googling) and it seems to work just fine. I also like that the FLR lens seals the optical back from dust etc., something I never thought of, it's kind of dusty here...

I was really trying to get some decent-quality magnification in the 50X range, without having to largely upgrade the back optics to make fancier EPs really worthwhile at this point. Likely in the future though. I'll report once I get to test it, for closure.