I think most of us, with a big bang and the roof gone on the cabriolet, would be starting down pdq and stuffing the mask on on the way. Don't forget we are talking '2 crew' here. Not a lot of point in the other memory items either, is there - eg motor the outlfow closed etc. If you are really worried about this "40000ft" thing, think how long it is going to take you to be 'safe' below 40?
With a slow rise in cabin altitude etc etc you could be a little more relaxed, I feel?
Conversely, the thought of you sitting there level at 41000, putting on the mask, establishing crew comms, selecting manual, motoring the valve while looking at the stars through the roof...................... 'horses for courses', as they say?