In reply to Dane1:
Good thinking Dane, I attach mine through cord anyway and your thoughts had crossed my mind too. On good ice, I don't use them, on mixed ground I am beginning to find umbilicals irritating with all the tangles around the rope, gear etc. Friends have had some success using a chest attachment point (8ft sling over shoulder, larks foot to harness, oh knot at sternum for attachment, oh knot under arm to take in slack).
My other worry with umbilicals is falling; fall on the wrong placement and the umbilical catapults your shiny sharp pride and joy towards your soft bits, ouch!