Welcome to the forum and glad I could help. Are you also establishing a manual switch too? On mine I considered what I think you are doing I.e., actuate reverse and back up light(s) come on? As I use my back up light for more than backing up I wired mine manual through fuse block to auxilliary battery. In this way if it gets left on it will run the aux battery down only and not effect the starter battery. Ideally a 3 way switch would be cool, off, manual on and auto on when in reverse. However I didn't feel the need with an aux battery and LED VisionX rear light.
jrc