be care full anything you wrap around the hulls doesnt flap in the breeze as this will cause more damage than a couple of stone chips. Any dust, dirt or even the texture from carpet or cloth can "sand" your hulls on a long trip.

I'd just go with the mud flaps idea. And get the boat up off the road a bit, put some risers under your cradles.

I've never had any rock or debris damage my boat on a road trip. Most of that stuff is deflected by the towing vehicle.

Bill