I think some setups will do it more than others, some trucks will push/pull me more than others. I actually get it worse from Uhaul style trucks than full size tractor trailers. It's mother nature and I don't think there's much to fix it. It's not sway, it pulls my whole setup in as one. I'm not disputing the Hensley guys at all, I just don't understand how it's a hitch issue.
I still go back to the speed differences being a larger factor with the OP, not saying he should speed up, but with a 15-20 mph difference he's going to feel something, regardless of truck, trailer, hitch setup. Pull over on the shoulder of the interstate and see what a Honda Civic feels like going 75mph right beside you.