RAT 5
I know of no Airline Staff that do 4 on 4 off, especially early and late mixes. I know plenty who do 2 days and 2 nights (12 hours)
then 3 off, and quiet a few who do lates /early combinations of 8 hrs then 2 days off.
Cant see a problem with crews doing 5 and 3, you might be tired on day 5 but so am i after 14 days with only 1 day free. and many of you are paid to work on days off. There's a major difference to being tired and fatigued