realskiers

Head has changed the boot designations this year; with probably not many if any technical changes.? S10 is now S11 and S12 is now S13. jBoti is 'bang on' on the shell length. My 26.5 are 305 mm.
From previous years S10 and S12 had the exact same liner; with only minor shell differnces.? You do not need stiff Flex with modern ski technique (PMTS); but you really need is lateral stiffness and not rotary forces from the hinge when you do flex.? The Head line is a wonderful 'lateral' stiff boot that does not part any rotary forces.? If you are not participating in masters' or other racing series you probably should stay with comfort and avoid a high stiffness in the Flex rating.

Good luck with your selection

Dave T