I have Jay's reducer on my 07 1200GSA. Yes, I got head shake, not serious but SWMBO got unsettled if I relaxed and allowed it to occur. I ended up putting a Scott's damper I had on another bike. I had trouble finding a mount and ended up with a mount made in South Africa that didn't fit the bike. I had to re-work that mount to finally come up with something I've been very happy with. Since I've done all of that I've seen the Ralle-Moto Damper and mount from another thread which to me looks top notch!
Here is a linky to the thread:http://www.advrider.com/forums/showt...teering+Damper