Cheers Biscuit and Chris for the replies, looks like I should have started climbing again a while ago! According to Dave Mac's article aswell I get the impression as long as it doesn't hurt you can crank open handed as hard as you like.. Bit worried of a sudden loading from foot slip or accidently throwing in a crimp so might stick to the easier climbing and crank on the open hands on the finger board.
Thanks again for the advice,
Mike.