i think and I have always done my light switches on the ground side, if something was to go wrong you loose the low beam, nothing else. Not fun seing sparks or smelling smoke when the switch goes up in flames when a hot lead gets wet.... trust me i learn that long time ago, i also recomend putting the switch on the left inner panel, in case you need to go dark in a hurry at speeds. that wait you don't have to remove the hand from the trottle at all,
Use the black wire to the ballast.
here is the simple version
the red wire goes to the hot side on the bike headlight plug,
the blk wire goes to the swith Off position
then another blk wire goes from the bike headlight plug to the on position on the switch,
done deal and no worries about getting wet.