Balancing my 30 MK I C&C
The C&C 30 MKI is one of the stiffest boats that C&C has designed. Check out this link to see how other C&C designs compare to the C&C 30mkI.
http://cncphotoalbum.com/technical/stability.htm
I've raced on one for the past 10 seasons and can definitely say that the stability numbers represented in this chart accurately represent the boat's characteristics. I've also raced other C&C designs such as the 24mkI, 25mkI, 25mkII, 27mkII, 29mkI, 29 mkII, 30mkI, and a 35mkIII and can say from first hand experience that their stability is fairly represented by the diagram as compared to each other. The C&C 30 MKI is a fairly quick boat considering it was designed in the mid 1970's. You should easily be able to carry a full main and 150-155% genoa in 15 knots true wind. If your sails are tired and blown out, that may contribute to your balancing problems. It's a very capable boat so don't be afraid to push her a bit.