trailer being pushed around by wind

Have a 29ft sunnybrook harmony and tow it with a 2013 F150 ecoboost with the tow max package camper is approx. 7500lbs and tounge weight approx. 800. the hitch is the reese with the trunion bar 1200lb and dual cam sway control, I set it up per instructions but when driving in a fairly stiff cross wind it likes to I wouldn't say sway so to speak but gets pushed around a lot. the truck sits approx 1 inch less than when its unloaded and the trailer is very level. it requires constant driver input to keep it in a straight line. I filled the rear truck tires to the max {44psi} but it didn't help much. I almost feel the tires have too soft of a sidewall and may be part of the problem? im not sure what to try next im hoping someone has something for me to try..thank you for any help also my old truck was a 2011 f350 and with no sway hitch you could barely tell it was back there!