Thanks Pleiades. I'd rather mount the relay under the seat , drawing switching power from the tail light wire, if that's suitable, (the Zumo's wiring harness is not easy to get into that close to the unit). Can I ground the relay to the frame or does it have to be grounded to the same circuit the switching power is coming from? Should the fuse be between the relay and the battery, or upstream of the relay?

Thanks again.