Dear Mred: I wonder if you have a trouble with your tonearm/cartridge alignment on the past or today: is it something wrong with your tonearm/cartridge performance?
from this " manual ": http://www.vinylengine.com/library/well-tempered/arm.shtml
it seems to me that you can/could make the alignment but maybe I could be wrong.
Now if you must needs the thread tonearm " numbers " maybe you can/could try to contact Transparent Audio ( Karen Summer. ) that build for years the WT products or to Andy Payor ( Rockport Technologies ) who made some re-designs about, maybe they could help you.
Anyway, with the WT protractor you have the effective length ( from stylus tip on the protrator to the bearing center ) and you have too the " mounting distance ( spindle center to the bearing center )and for subtraction the overhang and you say already have the offset angle. Of course that you have to make/take, with the right measure tool, those measures.
Anyway, it is almost incredible that the world distributor of WT can't answer to its customers.
Regards and enjoy the music.
Raul.