My hitch has developed some play at the point where it is pinned to the bed rails. It clunks when you stop and clunks when accelerating. Not bad, but enough to bother someone as anal as me. It seem...
My thought would be to fix the movement in the pinned area, not try to mask the noise. The more it moves, the more it beats that area up and the more it will move. Pretty soon you could have some serious movement. Fix it while it's small.