I was about to post the same question!
My lo is 10 months, and has only slept 11 hrs a few times and 11.5hrs once. He had been going to bed around 7:15 and waking at 5:45 for a while, which I decided was and early wake .. so tried the suggestions to stop this - cut his morning sleep to an hour (usually 1.5hrs +) and made sure he wasn't going down for it too early even if he woke very early. I tried it for a week - he was very grumpy, and started waking up even earlier (due to being OT I guess?). So I decided to stop doing it, but to push the nap start times a little so that he could wake from them later and go to bed later ... last night he went to bed at 7:45, asleep just before 8 and woke at 6:15 this morning.
I am fairly happy with this (prefer it to 7pm - 5:30am!!) but I am concerned that he 'should' sleep longer at night ... clearly he makes up for the shorter night sleep in the day, and even with trying to shuffle this around it hasn't worked so should I just leave him alone and hope that once he starts having less day sleep in the day/one nap instead of two, he will naturally sleep longer at night?