Use your vang downwind
I see too many Rhodes with their boom angled up and bouncing around downwind. The top of their sail is twisted off and wind is spilling out.
Use the vang to flatten out your leach and keep your boom stable. The top batten should be parallel to your boom in most conditions.
In very heavy winds, keep the boat under control downwind with more vang to prevent the boat from spinning out to leeward (death rolling).