For anyone who'd like to roll their own wide-angle TL120, I
offer the following dimension into the archives:

The rear flange of the shutter of the Mamiya C220/C330 55mm
lens should be positioned 13.46mm in front of the _back_ of
the standard steel lens board. For example, if you were to
cut a couple pieces of plastic pipe, screw them to the
standard flat lens board, cap each with another piece of flat
steel, and lay the whole thing flat on the table; the upper
surface should be 13.46mm above the surface of the table.

When so placed, the 55mm lens should be at the f/22
hyperfocal position.

--
John Thurston
Juneau, Alaska