Hot dog you're spot on. Depressurising the cabin....no, as you correctly said the outflow valves will modulate to maintain cabin px. The whole intent was to as black hands correctly stated was the swiss cheese model and it does beg the question 'How close is QF to a hull loss'. Why I gave the oxy and door seal a go was about ten years ago a 74 made an atb. The upper deck door px seal gave way and fogged up the upper deck. The tech crew wore oxy masks for the return trip home.