I'm registered on there, haven't posted much but I do use the cncphotoalbum list. Your MkIII is one of the more tender boats C&C produced, fast in light air though. This is quite an interesting chart if you've never seen it before, http://cncphotoalbum.com/technical/stability.htm
shows the relative stability of their various models. C&C never referred to the various marks in the way we know them, they were the MkI, MkI tall (Mk II to us), MkII (which covered the Mk III and Mk IV) and then the New 27 (Mk V).