I will probably make a small lens board for it to fit on the 6x12 then make a 100mm square lensboard as an adaptor which will take the small lensboard to fit on the Graphic.

That's the joy of having a CNC router and a laser cutter at work. I can try lots of these ideas out!

For focussing on the 6x12, I'm reminded of the "idiots' guide" of single person, group of people and mountains as seen on many simple cameras such as my Olympus Trip.