IME you can't cook to a specific time, you need to cook to an internal temp. I usually cook it till the fat cap starts to split (about 4-5hrs, maybe more), then wrap it in foil & cook till you get an internal temp of 200F & then let it rest for about 30-45mins. Mine usually take about 8-9 hrs but it has taken more for larger butts.
Jeez, if you want it ready for 11am then you best be putting them on about 1-2am.