In reply to GridNorth:
> With regard to sending the fat lad down first, it doesn't really make me feel any more secure. I don't know if there is any evidence to suggest that this is safer. He may have just weakened it.
I actually know of a case in which the anchor failed after the fat lad successfully went down first. The climber who fell survived, although he went down a snow chute, over a cliff band, down another snow couloir, and stopped just short of a huge cliff band that would certainly have been fatal.
Although I don't bother much with sending the heaviest person down first, I'm a big fan of the non-load-bearing backup for everyone but the last person down. I should add that having done this many hundreds of times, I have never had the in-situ anchor fail and the backup come into play, but may be because I don't use the backed-up method on really bad-looking anchors, I just redo those.
It is possible that the backed-up rappellers add just the load necessary to cause the anchor to fail for the last person, but I still think this bit of very bad luck is unlikely and that the backed-up test will usually be decisive.