"Porpoising" - How to Tame the Rocking Camper

I would start with the easy stuff. First check and see if the bottom of the camper and the bed of the truck are both flat. Then I would put it on a scale and see what all the weights are front back and total. You could also measure if your frame flexes when you load the camper. You can also try loading the camper in different spots. My truck seems to ride better with the camper a few inches back and offset to the passenger side.