I also used HVMP heavy, but machined to size/shape of the original, with universal mounting. I sispect the compression on the universal mount inside the handlebar also helps in terms of reducing buzz. I have been very happy with the HVMP. My project originally started because of unequal bar end gaps. Here is the thread showing my solution, and has a link to an easy way to remove the stock bar ends and inner weights.
http://cb1100forum.com/forum/showthread.php?tid=11229