Some insight from a long time FDXer. Do not under appreciate the ill affects of back side of the clock flying. You do adjust (as a trip proceeds) but I don't think anyone really adjusts, and after a week or so of home time, its back to square one. Many posters on here that work for FDX or UPS, looking at the glass half full, will point out that day flying is there, when you have the means to bid or trade into it. True enough, but with so much night ops as part of the system form, you can't really get away from it unless you subjugate your seniority and schedule totally to avoiding night trips.
The thing I have always felt was scary about hub turns were not the normal rotations that are scheduled. The union and company work together to minimize the worse pain that the CBA will still allow. The bad is just how ugly any given duty period could be if events push a day to operational limits. At FDX we have contractual limits short of the FARs (which cargo did not get the 117 improvements). It is possible to start a duty day at say, 1900 and finishing at 1100 the next morning. Even worse, you could start at the hub at 0200 (did you sleep before driving or JSing into work??) and run to 1800!!
Does it happen? can you pull the plug after getting the run around? Yes you can call fatigue, but just having to shows how bad things could be with back side of the clock ops.