@aupatking well, first of all, I cheat. My ski partner Terence Fogarty (then with business partner Jenn LaPoint) patented the rotationally adjustable binding. Everything I know about binding rotation I learned from them (and some from KLP).
As for measuring, the centerline of the plate is scribed on my Fogman plate. I have a “centering ruler” that I bought at Michael’s craft store. Zero is in the middle of the ruler, like where 6 would be on a normal ruler. Increments are 1/32” so I can put zero on my centerline and quickly verify that my centerline is actually exactly in the center of the ski. Then I can accurately measure my toe and heel distance from center. So adjustments are precise rather than eye balled.
@coach3 Once you have your fore/aft binding location and fin adjustments dialed in, binding rotation is the last fine adjustment to the roll of the ski. For example, I’m LFF and I rotate my front binding toes right, heel left. By doing this, I move my left knee to flexing over the center of the ski rather than quite left of center, which is where it goes if my front binding is fully centered on the ski. This moves pressure from the outside of my ski on my off side turn (“high siding”) to the center, allowing for increased roll on the inside or turning edge of the ski, tightens up the radius of the turn, and balances the turn radius with the on side turn. If your knees naturally flex over the center of the ski, or your turn radius is naturally balanced side to side, rotation may be less important.