I have heard that some people run whole or part balsa foils. How does this affect your overall performance (gains & losses) as well as do they tend to crack or distort after a capsize?
Quite a number of SA boats are running Balsa Core Rudders, not sure about C-boards. Macca Hazelgrove at Yachtcraft makes them, and some make their own.
An alternative to Balsa is Palownia, almost as light.