The vibration seems to be a pretty well-known characteristic of this bike - at least, I've seen a bunch of threads on other forums about it. Solutions that seem to be recommended most often are gel grips and bar ends. I haven't tried these options yet but probably will next season.
For more info, try this thread from the f800 riders forum: http://f800riders.org/forum/showthre...eds-over-80mph
Good luck - and please report back if you find something that works well for you!