I went a different route (as usual).
I mounted a flood light under the trailer to light up the tires and the sides for backing up. Also works if you have to change a flat in the dark.
I saw this picture in another post and plan on doing the same thing. Both the flood under the trailer and the loading lights will be switchable from the trailer and come on when the truck is in reverse. I really like the idea of having light available for chaining up or tire change. Have you had an issue with the road grime? Wondering if I should make a mini mud flap to put in front of the light.