Some V-speeds related to performance are at speeds determined by the shape of the drag curve. Vs is not one of them -- it's related only to lift, not drag -- thus it doesn't appear at a particular point on the drag curve. It's convenient that your EADI gives you Vref (or Vs) for any configuration and weight, but unfortunately you can't use that to get a minimum drag speed that is similarly corrected, because Vs and minimum drag speed are not related.
If you know the minimum drag speed for a particular configuration and weight, that speed will vary with the square root of the weight. So a 2% change in weight causes a 1% change in the minimum drag speed. There's no easy way of assessing how minimum drag speed varies with configuration.