You can spend a lot of time milking out the last degree of dwell, button it up, go around the block and you lost some.
Dual points give you more dwell and a little more bottom end torque.
The tension in those points wears the rubbing blocks faster then a lo-po single point.
Just use the feeler gauge, go/no go on the high point of the distributor cam with .021, put felt wicks on the points, use point cam grease and leave them alone.
You will wind up running about half way between the maximum dwell possible and the dwell of single points. That's all they are intended to do.