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You can get a 11-36 11 speed cassette right now through any Santana dealer. Bill McCready built some custom cassettes to Shimano specs in 11 speed. He had a complete 11-speed drive train at Interbike using the 11 speed cassette and K-edge rear derailleur modification and has even adapted Dura ace chainrings to his carbon cranks. He was able to match up the dura ace esthetics quite nicely. He is a running an 11-speed cassette body on the a set of spinergy wheels. It shifted very nice in the stand . He has been a strong proponent of Di2 since its inception. I am going to get a cassette body for my wheels, a cassette, an 11 speed derrailleur and move my k-edge cage and upgrade my system to 11 speed and all the rest of the components will work fine. you will need the K-edge cage for the rear derailleur if you want to run an 11-36 cassette as even the Gs cage version will only run an 11-34 at best according to Shimano tech reps.