I elected to not get the WD on my OFF-ROAD POPUP trailer. It weighs in at 4200LBS loaded...
I guess the fact I have no wind resistance with everything tucked away behind my F150 truck helps matters big time. I have been all over the southern states and as far West as Texas - Okla pulling my POPUP trailer with no issues what so ever.
I have even been hit with the wake of a hugh log truck speeding on a two lane roadway in Arkansas near the Georgia Pacific Wood Plant... One time the wake was so bad it blew off one of my Ham radio antennas mounted on my truck...
My POPUP trailer tracked just fine... My F150 has some kind of electronic sway control that probably helps as well.
If I had the taller TT type trailer I think I would want to use WD like others has said on here. I suspect My F150 truck probably would not be enough truck to pull those larger trailers.
Roy Ken