My experience is a "core" of say 11-4 works better (you'll get 8-to-4 people and 11-to-7 people, contingent upon your having a good mix of morning and afternoon people).
The underlying prima donna problem you've got makes me think no matter what you do your devs need a talking-to by top brass along the lines of "You're here to help the company, and right now the schedule ain't workin' - shape up or ship out"