Just getting started on this, so nothing to show yet. I have a metal adapter plate that mounts into the 679 back (or front for that matter, but then I'd have to mount the lens on the back and focus with my left hand...) and a couple of Graflock backs so now I have to 1) cut a bigger opening in the adapter plate, and 2) conjure up a 3D printed adapter to put between them. Open to any suggestions.

I'm thinking that arranging the back in "landscape" position would work best to avoid potential issues with rear tilt, but haven't measured enough to know if it really matters. (I know, I know, landscape vs portrait for 4 x 4 is sort of like complaining about why my Hassy V doesn't have a tripod socket on the side. Come to think of it, though, I sometimes do use it on its side when I want an eye level perspective and don't want to use the prism finder.)