The more lights, the better, IMO. Legally, if the back of the car (or the load in the pickup, etc.) extends more than 6 feet from the face of the rearmost light, you need a red flag or another light. I would prefer as much warning to the sleepy driver behind me as possible. Pick up a set of those portable magnetic lights that can be tied into the dolly lights at the hitch mounting point (if your car has metal fenders/deck lid vs. plastic body parts).
2018 THOR Chateau 35SF
Two Labs, Bugsie & Blondie