The best way to prevent wing rock on your UCD........sell the UCD.

Sorry but you did ask for the best way to get rid of wing rock.

But alternatively you can cut the wing tips off and that will help tremendoulsy. I cut the wingtips off my Flip and it was then able to harrier and elevator with much much less wing rock. My buddy them tried the same mods with his UCD and had the very same success. But I still say the best way is to get rid of it