I've now done a couple of these. I still remain a bit unconvinced. They're certainly not great. But, 'unsafe'? I'm sceptical. The 5231 is significantly better than the alternative, if you have the option. The cabin crew are definitely up in arms and the vast majority filled out fatigue reports- on both flights. However, these were the same crew that spent the day we arrived out sightseeing. Both flights. The problem, as I see it, is precedent. Had a look at the number of Fatigue ASRs generated from JFK? Seattle is similar timing but three extra time zones and a 'normal' sign on time. I certainly would appreciate another 24 hours but I'm not convinced it's a necessity and not a desire.......