I was at the Mor-Ryde site and they have different videos about this chucking problem. As far as my setup with my 15 year old hitch, and the F250 I have no such problems.
My previous 1/2 ton and 1/4 ton trucks and smaller trailer created small chucking, I blamed it on the weakness of the springs allowing the drive train to vibrate under load.
Thats why the dragsters have rear end bars to hold it straight. We have to realize that our TV's are not on a 1/4 mile strips, they are on an ever ending strip and at max power at every hill.