Hi everyone!

I'm just getting into ULF, and recently acquired a great Rodenstock Apo-Ronar 600mm F9 lens (the older version, not the CL). The only thing I don't have is a flange for it, however, it was just too good of a deal to pass up. I've looked on some other threads here and know that SK Grimes can make a custom one, but I want to see if I can find something that will work before going that route. Anyone have any ideas for finding a flange? Alternatively, is there a lens board that would work? After doing some other research, I think the non-CL 600mm that I have uses a M90x1 threaded flange of overall diameter 121 mm. Please correct me if I'm wrong! Thanks for any suggestions!