you would have to interrupt the power before it gets to the switch for the headlight. The switch changes the + voltage for the high/ low beam. The tail light is circut is not affected by the headlight circut, so it would have to be interrupted on its way to the tailight. If you cut the power at the stator, you also loose instrument lighting and hand/ thumb warmers. A DPST switch should do the trick (double pole single throw) I Dont want to know why....