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.

A 20 degree canted dagger board is going to produce approx 30kg of lift at 15 knots but will probably be within 0.5m of the LCF so this is the equivalent longitudinal righting moment of just 7.5 kg at the transom. The 30kg is 20% of an A cats sailing weight, 16% of a one person F16 or 12% of a two person F16 (canted boards are not allowed on F18). The wetted area reduction on the one up F16 will be about 10% however both the dagger boards and the rudders are now bigger than was necessary without canted foil and as a result have increased their drag diminishing the return.

So whats the net result...(on an F16 because there are more options).

Hull and foil drag at down wind (less to more)

one up with canted foils.
one up conventional.
one up adjustable rudder foils = two up conventional.

Resistance to pitch pole (safest to most dangerous)
One up adjustable rudder foils = two up conventional
One up Canted dagger boards.
One up conventional.

The above is supported by the move in A cats to canted and/or curved foils as it shows a definate advantage in that setup.

The next question becomes what is more important top speed or resistance to pitch pole? As that will decide the future direction of the F16 under its current rules.