Dan, I couldn't get the link on my computer for some reason (it has developed a number of issues recently) I just got it up on my wife's and page 8 ansers my question so thank you.
Jim, thanks for the references, I managed to find a copy of Jim Stone's book.
Brian, you are dead right, I'm thinking out loud and having trouble just working out how to post on a forum which I've never done brfore let alone decide on what view camera equipment to purchase! Thanks gentlemen.