I don't know that Ive ever seen one....I think it would be a good sized hassle to get to run right... if you had easy access to a dyno, i think it might be cool, otherwise, it would be a constant head scratcher.
I know alot of folks say the dual carbs are a pain, but I always liked them...
If I were to do it though, Id go with the mikuni... so much easier to use/tune/repair.
Did see them on banshees...helped my friend put one on. he HATED it, and went back to stock the next day