It's a good argument Luiz, and one I'd be far more likely to use on a boat than the over complicated rudder foil system discussed above. The problem from a practical point of view is that the application is limited by pretty much all the cat classes's rules.
This configuration is used downwind by ORMA 60s, BMW Oracle, Hydroptere and the like. I just put the concept in words. My boat is far from their leagues, but the configuration is similar. Note that they are all trimarans, not quite the same as beach cats.
Still, Bill Robert's ARC20 features smaller daggerboards forward of the main beam and slightly larger rudders. He says that both the increased distance between the foils and the smaller difference between their areas result in lower total drag (besides shalollower draft, naturally). Turbulence / interference between daggerboard and rudder are not an issue in trimarans, so I guess a beach cat benefits more from this configuration.
Rules suck. Show up with improvements that result in significant increase in performance or seaworthiness and the rules will follow eventually.
