In reply to drsdave:
6mm cord is going to have a breaking strain of around 750kg, roughly equivalent to 7.5 KN. There may be some advantage over a sling because it may be more dynamic, but also loss of strength because it has to be knotted.
A factor 2 leader fall could generate 9KN at the belay.
Assuming you have 2 or 3 pieces of gear placed, in appropriate positions and well equalised with loops of the cord this is obviously safe (especially since small pieces of gear may be rated less than the 7.5KN cord anyway, and some nuts and hexes may be tied using 6mm cord).
The main problem comes if it's not perfectly equalised and one strand of cord comes into play before the others. It's highly unlikely, but that could be 9KN on a 7.5KN strand of cord (rather than on a 22KN sling or better still a length of the climbing rope itself).
There is also the risk of knot failure / slippage, which you should be able to avoid by tying correctly but which is largely avoided using sewn slings or the climbing rope.
