I have started to adjust this lens head for Nikon F mount, I shaved ~1mm from the top of the helicoid. No infinity yet.
This one goes from 11mm to 18mm, in stead of 12 to 19mm. The head + this helicoid + M42->F adapter makes F-mount
G-Sonnar 90mm, also it can be used with EOS_5D by using F->EF adapter together. MFD of this F-mount will be ~1.7m.