In reply to traderdb:
The standard practice in rigging is to use dynamic rope for cow's tails to lessen shock loading in the case of a fall. (if you are clipping in below waist level, then fall arrest shock absorbers are also used but that would be excessive for your purpose).
Looking at the results of the DMM sling drop test, all the FF1-2 results show shock loading of over 10kn, which would risk internal injury, even if the sling doesnt fail. You are in a very short system when using cows tails, so high fall factors are quite possible.
Guess its a calculated risk - an increased safety margin on easy ground vs not carrying extra gear up there when a sling would suffice...