In reply to UKC Gear:
I've used a Beal Gully in the Alps a few times, each time in combination with a thicker half rope. The Gully is a bit fluffy now but holding out ok for the time being.
I've used it on routes where you need two ropes for the abseils but one rope suffices for the climbing - so the Gully either stayed in the sack or was used in half rope mode (the original idea was to use it on the Integral for the Noire abs - still waiting for that!).
Not sure I'd be brave enough to climb on two 7.1 - 7.3 mm ropes - not likely to fall in the Alps but plenty of sharp edges and falling rocks...
7mm cord would be a bit lighter and I imagine still ok to ab on in combination with a thicker half rope (as opposed to using it as pull cord) but there's obviously an advantage in having a second rated rope.