Wow! Great info and suggestions.
Things I've learned:
1) It's all my buddy the road way engineer's fault!
2) More specifically, it's harmonics between speed, placement of the joints, and wheelbase of the rig.
3) Solutions are to adjust speed or stay off those road segments.
4) While only my buddy the engineer can fix it for good there could be things that could improve it.
Speed Adjustment - not sure I'm comfortable driving through it to go faster. The speed limit on most of the stretch is 65 or 70, and that's where it happens. I'm not comfortable towing faster than that, so I'll need to slow down.
Better shocks, air bags, Timbrens, Mor/Ryde, tires were all suggestions I saw as ways to help.
I think my first attempt for adjusting it out is going to be checking the hitch setup using the instructions I found here (and calling the vendor if I don't understand something). Second to that, Timbrens look like a fairly inexpensive and easy to install solution. Before I start throwing money at solutions does anyone else have experience with those? I would guess I'm looking for something like https://www.etrailer.com/Vehicle-Suspension/Chevrolet/Silverado+1500/2018/TGMRTT15S.html?vehicleid=2018306592
Thanks for all of the great advice and suggestions. I'll report back on the thread what I find with the hitch and receiver. The longest trips we're doing right now are 150 miles out or so, and there is only about 25 miles or so of this stuff. My biggest fear (aside from tearing everything up and hurting people) is getting on a stretch of 250 miles of that stuff and dying from old age before getting through it! But, I guess the best of all the suggestions may be to get off of those roads!
Thanks, again!
Dan