I picked up a Corbin seat that was made to move the driver forward an inch. I then picked up a backrest for it and discovered it was an inch behind me when installed. I stopped by the Corbin store in Florida only to be told there are no devices to buy from them that will give it a fore/aft adjustment. They did say I could get one with more foam on the front to compensate.
I was annoyed and decided to mod the one I had. After I did the work I still was not happy with it. I needed lower back support from it not half back support. Deciding I needed to find a backrest that I liked and doing the mod again was what I needed to do.
I now have the setup I like for the rider and used the Corbin setup in the rear. I really don't like the functionality of the Corbin back there because it's too large to place my helmet over it when I park. I am going to get a Harrison Specialties 7 x7 backrest for that purpose. WOW. I can't post pictures.
. PM email if you want to see them
