next after Upper Stableloads? Jittery ride on rough pavement

Hmmm.I usually relate jittery to unladen ride on rough pavement. As mentioned, there are certain road surfaces that just suck.

Not sure why you are opposed to lower SL’s. I am running upper and lower SL’s on the new truck and am VERY pleased. Nice firm ride when loaded and 100% stock ride unladen. Couldn’t be happier.

Have you been to the scales? Maybe you need to get some weight forward?
Where’s your water tank? Try a full tank. Sometimes that helps. A front hitch with some junk on it can help also.

Safe travels, bill