The extra tab underneath the VR is actually on the same post (#4) as topside. (and, of course, insulated from the housing).

I do have the dash panel with the ammeter, temperature, and oil pressure guages. Could I use that ammeter in the charge light circuit? I was going to use aftermarket guages, but if these would work....
Otherwise, I will do as you suggest with an ammeter in the main charging circuit.