I would say they do not work. Just look at the trucking industry. If they worked you would see them on those rigs. Back in the day those big wings that go on the truck roof to direct air over the camper were the same thing.
The best advice i would give you is to make sure your equalizer hitch is properly adjusted. It should put weight on both the front axle and rear axle of the truck and some back on the trailer axles.
Also run a GOOD sway system. And remember you have a reservation at the campground - take it easy and enjoy the ride.