[CB..]

it may well be that the stock crew fatigue set up would be the place to experiment...as with very little imagination you can simply include rationing in with the concept of fatigue...if you slow down the stock fatigue rate and switch off the "rest room" so the crew do not regenerate then a finite length of patrol can be set up....do a search for fatigue ..there must be pages of posts on the details and editing of the fatigue settings