Just to (hopefully) clarify, it helps to realize from a drag perspective, all things being equal and ideal, that the optimum is two boards (1 rudder + 1 dagger) of the exact same size, at the same angle of attack.
Also, this necessitates the center of effort intersecting the middle of a line directly between the two boards. The further apart the two boards, the less effect the shift in CE has, the more "balanced" the boat. Voila.
Of course this all gets screwed up by the hull and daggerboard being locked together, the board being adjustable in area (unfortunately proportioned to aspect ratio), and the rudder being of fixed area, but adjustable in attack angle, and wind strengths varying.
Humbly Submitted by a Talkerabouter.