With respect to the counterexample you are giving in your post :
A daggerboard with 1 sq. mtr. area and only 0.25 mtr depth is far out rediculous. It would have to have a daggerboard well that is 4 mtrs wide to result in that area. That is not a daggerboard, that is a skeg.
Sorry Simon that counterexample is beyond ridiculous and I won't take it seriously.
It was not supposed to be taken seriously ! It was to illustrate that someone could build such a boat (that measures as a F16) and then turn up to an open Handicap meeting and (correctly) claim a rating of 1.05. It's a (IMO) missing component in the rules of the F16 (and F18) that the plate is not controlled more. As you say there is a relation between sail area and plate area (square or cube root of sail area / 100 I think, or something like that !).
