From the front page:

"...One of the problems with the Inter 20 going through surf is their rudder blades are so slim -- very efficient when down and moving, but not very effective when partway up."

I'm not sure I agree with this statement. Yes, the blades are thin and it does slightly hinder maneuverability at low speed or when partway up, but I think the biggest problem is the whitewater they're sailing through.

Because of the turbulence (and amount of air bubbles in the water), there is not really anything for the foils (fat or skinny) to "grab on to" and establish flow. No flow=no lift

I experimented with windsurf skegs years ago, and even the very fat ones had no "grip" in that kind of shore break. Once you got into solid water, however, the fat skeg did establish maneuverability slightly faster.

Maybe you nautical engineer types have suggestions on how to maintain steerage in this 'washing machine' condition?