I customer who just had knee surgery asked if I could modify his Shimano Ultegra Di2 (6770) rear derailleur so he could have more gear and go up to a 32 tooth rear cassette. I replaced the standard SS cage with a new mechanical Ultegra GS cage. In addition to this change, a longer B-screw was needed to provide clearance between the derailleur and the cassette. Worked out perfectly!
Old SS cage on top and the new GS cage installed on the Ultegra 6770 rear derailleur.
