Many thanks to those who supplied constructive answers to the questions (mighty gem, fijdor, flying binghi, ascend charlie, arm out the window) and to those who gave amusing anecdotes, useful insights, etc. Fewer thanks to the handful who took the question as an opportunity to wave their (presumably diminutive) body parts - one in particular who I've now blocked. Just because you think it's a silly question, doesn't mean that I - or my friend - are about to go and do stupid things. But then, this is Pprune.