If you want a single pole I can draw that up for you. I don't like switching the positive, it's noisier in an electrical system, but obviously the OEM's do it all the time. You will note that both the coil's switched 12V and the ground now goes thru a pressure switch, different ones though. Only way I could think of to use a single pole relay without getting real complicated and expensive. Not to mention automotive grade relays are cheap and easy to find with a single pole.