Nice work!I DID IT!!!
The answer to the valve seat riddle was so obvious it's painful. If you want to make a small custom donut-shaped regulator valve seat, why not start with.........a large regulator valve seat? Duh.
I'm tempted now to resurrect my 2100B... I even had a stainless collar made up after my plastic one cracked like all the others but then ran out of other spares so its still in a shoebox somehere.
Any idea on sizes for the various body o-rings?