4x4 Lensboard and Screw Thread adapter for Large-Format Enlarger Lens

One of my nicest 4x5 format lenses is a 150mm f/4.5 Rodenstock Omegaron, so when I saw a chance to buy a 210mm version very cheaply, I jumped on it. It's a beautiful lens intended for use on an enlarger. However, when it arrived, I discovered that it is MUCH larger than the 150mm, and doesn't actually have a screw thread mount. Apparently, several of the Rodenstock enlarger lenses targeting 5x7" or larger have a rather odd mount with no obvious screw thread (see the right side of the last image above).

After some head scratching, I realized that I could 3D-print a screw thread ring with a split, so the ring could be pulled apart to mount on the lens and then would hold firmly together with a mating screw thread in the 4x4" lensboard. It works great. I also have a 60mm extension tube design here, although I haven't yet needed to print it myself.

Odds are good that other lenses have similar odd mounting arrangements, but probably with different details about the sizes, etc. So, unless you have an Omegaron 210mm f/4.5 lens, most likely this design will not work, but the same idea would still apply.