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[Mr_Roboto]

I'm just going to agree with all of the above.

I used to have a tow dolly, I think the tires held about 65 psi for towing. I would air them down to about 10 psi unloaded which cut down a lot on the bouncing. I had to run from Cleveland OH to Lancing MI with the dolly empty and didn't need it bouncing its usual 4" off the ground.

For a long empty trip, I definitely recommend airing down. A tire running with very little weight on it only needs enough pressure to keep the beads seated, like I said I ran 10 psi for several hundred miles with no issues.

Balancing the trailer tires will probably help somewhat. Also there are hitches that have a rubber isolator inside that may help isolate some of the vibration from your tow rig.