It is worth remembering it is a very big sky and a relatively small aircraft, so while you may create excitement if you do 'plunge' down unannounced, you are very unlikely to actually hit anything, and if you gotta go........................
Barker - remember we are looking at less than 20 seconds of 'useful consciousness' at those heights, and there will almost certainly be pax who have not masked up in that time. Also the effect of a 'rapid' will empty the lungs of most of the existing oxy, and the feed from the mask is going to be well diluted at that height plus the lack of a real positive pressure which as you will remember from the Ruddles-drinking course degrades the effect of oxygen - as you say we have no information as to how effective it is. Your 'monkey-swinging' crew could well be stacked in a heap in the forward galley, of course, if they risk moving around at the start
