Okay, adapting my Speed and GVII to take 96x99 boards shouldn't be hard -- that kind of thing is what 3D printers are for, though making an adapter that's less than a quarter inch wide looks like a potential no man's land in terms of the retention slides. I'll have to do some measuring.
A potential alternative might be to 3D print some mounting rings that are hand-operable to make switching a lens from one board to another less of a production.
Film holders I've got -- I think twenty or so, almost all Riteway plastic units (a few Graflex wood ones, maybe a couple of something else), plus three Grafmatics and the LomoGraflok, and an Adapt-A-Roll Six-20 -- I'm not new to large format, just want something with more flexibility than my Annie and more portability than my Graphic View II, with an aim to doing more large format landscape and nature photography.