Jake,
The technical committee of the I20 class has decided that larger rudders on the I20 make it a better boat. On an airplane or a sailboat when a foil stalls, it is being asked to generate more lift than it is capable of. The lift per square foot of lifting area exceeds the capability of the foil. This is called wing loading or foil loading and is measured in pounds per square foot, for example. There are two ways to solve this problem. Either reduce the load or increase the foil area. The I20s that I saw at the Steeplechase this past year had the mast leaned way back. I can see the rudders carrying a bigger load than they were originally designed for. Bigger rudders are required to carry the increased load.
Bill