Here is how I look at this. I never have seen a major rental firm that has dollies have lights on the the rear of the car.
I used a dolly for awhile before I went to four-down. I used magnetic lights on the rear. Here is why.
I have seen way to many dollies with one or both of the lights dead, how ever with the advent of LED lights the odds are improving.
My installing rear lights was strictly a safety reason on my part. Dolly lights, as you know, are low to the ground and out of the line of site of other drivers and may be partly blocked from their vision.
I felt that by putting lights on the rear of the car I increased the visibility of the towed and if I had a dolly light(s) fail I would still have lights. It also raised the lights height that (hopefully) the distracted driver might see them and avoid running into me. Kind of like the third brake light.
There is light cord Y's that are readily available at nearly any place that sells towing stuff. I used a short lead from the MH to dolly front then put the Y in the circuit and ran to each unit.
