FWIW, I replaced a ruptured vacuum advance assy on my W & H DuCoil (not a DuPoint) and I had to place a physical stop in the vacuum chamber to prevent advance past 45 degrees at 2500 rpm... shimming only seemed to change the rate of advance. 

Should I have simply re-drilled a hole in the vacuum advance arm/plate attachment point?

Cheers... Brian

Cylinder Index = 84

Current Experiment = `57 Tbird, Grand Rapids, Michigan