I'm sure I'm not the first person to think of this but... Whenever I haul my
canoe on top of my SUV, before I put it up there I slide on some foam pipe
insulation over the top of the gunwales. This protects my boat (my wife
calls it "our ship") from bouncing and vibrating against the top of the
luggage rack and only costs about $1.75 per tube at any home improvement
store.

Just thought I would pass it on.

Smed