I upgraded my components last year to the new Ultegra 6800 group. I want to repack the hubs, but I noticed that they use ball retainers rather than just greased bearings. I checked about getting those ball retainers, and I think I can find them for Dura Ace hubs, but not for the Ultegra 6800 hubs. Are the parts more or less the same? And, can I just put new bearings in and forgo the ball retainer? According to Sheldon Brown, you can do that and it's preferable, but it seems to me that Shimano used that method for a reason. Any thoughts?