Originally posted by treemonster
I notice you are not using a safety with those ascenders. There have been a couple of cases where they failed, and professionals are now using a short 10 mm line to tie a french prusic or some such above the top ascender. It secures the unit without slowing it down.
I think there is a little confusion about when to use a back-up with ascenders. With my setup both ascenders are life support anchored on my saddle so if one fails, the other backs it up. If I add a prusik backup I would have two backups for a theoretical single life support anchor (in case of failure). I think it is highly unlikely for both ascenders to fail at the same time so I'm not adding the prusik.
A known scenario for an older version of the Petzl ascender to fail is when the climber goes off vertical. In that case clipping a biner in the holes at the top of the ascender prevents it from coming off the rope.
I'm not familiar enough with some of the other ascender configurations but if you were using say one upper ascender or a Croll ascender attached at the chest and a foot ascender than you would want to add a backup above your waist. It wouldn't be fun to hang from your foot if the top ascender failed.
Thanks for thinking of my safety, and let me know if you still think I'm missing something, 'cause I'd like to know if I am.
-moss