Given that the RT-99 discs are centre lock only, what are the recommendations for lightest affordable hubs that will suit the centre lock system ?
I believe that is specific to the new 140mm Icetech rotors seeing as there are currently 6-bolt IceTech 160mm rotors available.
Not convinced that is accurate, I think I have seen 10spd Ultegra shifters working with 11speed DuraAce front and rear mechs. The shifters are just switches and the connections must be the same. The Ultegra 6770 shifters DO work with the new junction A and internal battery, that I do know.
While I have no experience, Shimano has been very forthright in promoting the fact that assuming components have been updated to the latest firmware, any e-tube Di2 component is interchangeable with any other within the limitations of the component. What that means is that if you have a 10-speed Di2 e-tube compatible group and want to go 11-speed, even though the 11-speed shifters will work with a 10-speed e-tube rear derailleur, there is not a firmware update to make the rear deraileur shift 11-speeds so this will also require an 11-speed rear derailleur and cassette.