If you're stuck with having to provide that kind of coverage, then it has to flow from earlys, to afternoons, to nights - then a beer break. I used to work that arse backwards shift and it was the dumbest way to spend a day I'd ever come across. As for human factors in general, its like pulling teeth to get the bean counters to accept it, especially as it only contributes difficult to quantify "soft" benefits to the bottom line. If your management views you as "labour units", the sophistication of human factors and organizational behaviour type thinking in your organization - is a long way off.