Trey,
I agree with you. I recently drove to Maine....about 7 hours drive time and my 11 month Newfoundland puppy..(if you can call 130# a puppy), got more and more restless the longer we rode. And this was 98% steady highway miles. He's ridden on the beaches in the winter and spring with gentle ups and downs along the shoreline at 70 mph always soft landings in the soft sand, and he seemed happiest when we weren't travelling fast.
I have an extra large Kurgo harness tethered to the middle seatbelt which allows him to move a bit, but the longer we're in the truck the more antsy he is...
Eddie