I discussed the details for building a pass-through extension ring for the Z system with my friendly Nikon repair tech today. My aims are of course firstly the 50/1.8S, and secondly the mighty 58/0.95 when it arrives. We went through all the technical part drawings (which I cannot reproduce as they are classified) and decided upon the parts required. They are now ordered and should arrive within a few weeks' time.
Afterwards, I snapped a photo of him in the bad tech-lab lighting and he did a complimentary free cleaning of my Z6 ... which was a bit more dirty on the sensor than I had thought.
It obviously pays to build and develop relationships.
(24-70, Z6)