Just a thought... Last year I purchased some "Air Tabs" (just google "air tabs") for our fifth wheel. I believe I have less pull, side-ways with them installed. I drive a dually, so I have never felt what I would call "motion", either when passing, or being passed in either direction! But I can tell there is a pull. I had also hoped for slightly better fuel mileage. What I will stop short of, is an overwhelming endorsement of this product. I believe they cost too much to be worth the little improvement observed.
Just my opinion...