I've read in the Graflex repair manuals (but have no personal experience) that these kind of shutters need to be pre-tensioned to a certain degree before the shutter tensioning mechanism is is set to its lowest number and replaced. For the Anniversary Graphic, it's something like 6 turns, tehn re-set the tension counter to '0'.
Have you considered contacting Fred Lustig (Reno, NV). Check Graflex.org for his contact information. Hopefully his health is still good enough that he can help.