I can say with experience that a 6/6 schedule out right sux and is downright dangerous. You never get an appropriate amount sleep with this schedule.
Any other schedule not using either noon or midnight as a base point for the crew goes over like a fart in a space suit when drills come up.
It is hard enough getting them to try new things (newbies), willingly participate, and pay attention, then you want to cut into their sleep time?