You can prove the tongue weight theory easily. Make a base line run and note the speed at which the sway begins. If you have a fresh water or holding tank in front of the axles, fill it up. If you can't do the water put something heavy inside and as far forward as you can. Case's of soda, can goods what ever but it needs to be a couple of hundred pounds.
You could also unload something from the back but this would take twice as much weight for the same result. Now go for a spin and if tongue weight is your problem the speed at which sway begins will be higher.
