I actually have the add on Air Bags on the rear leafs of my 2000 Full Size Ford Van towing vehicle.
Got something with a little extra tounge weight or maybe something heavy in the back of the van?
Just add 25 to 40 psi in the air bags to bring things back up to level. And they are independent from side to side so it does not make the body roll going around the corners.
Makes a nice hauler along with the custom made tucked up 2" receiver hitch.