If you see at the very bottom of this pic, I have my license plate mounted on the crossmember that is rearmost connecting the frame rails to the skidplate.
I have it zip tied directly below my license plate for now. My electrical connections for my runway lights are right there by the Port end of the frame rail (by the tail light). so it was easy to mount the switch anywhere within it's wires length radius of that point.
I zip tied it for quickness and in case I have to move it.
After we pulled out of the water, the lights stayed lit as we went up the ramp, but were out on cue in a minute. Test was successful. I'll have an override switch later in case I want my "ambiance" while wiping down the boat!