Without requiring the hulls to be symmetrical about a plane, there is no way to define the hull's vertical plane. Also, is someone tried to turn the rudders, they would no longer be in the plane. To begin, some definitions:

A. The rudder plane is the rudder's plane of symmetry.

B. The rudder plane at rest is the rudder plane when the rudder is angled so that the rudder plane is parallel with the boat's longitudinal axis (an ERS defined term).

C. The daggerboard plane is the daggerboard's plane of symmetry.

D. The daggerboard plane at rest is the daggerboard plane when the daggerboard is angled so that the rudder plane is parallel with the boat's longitudinal axis.

I would write the rule with a combination of these three rules:

1. The rudder plane at rest and the daggerboard plane at rest shall be parallel to the boat's longitudinal and vertical axes.

2. The rudder plane at rest and the daggerboard plane at rest for the daggerboard and rudder on the same side shall be in the same plane.

3. The head of the daggerboard when fully retracted and the tip of the daggerboard when fully extended shall not protrude beyond the beam restriction.

I would also add a few more rules:

4. No part of a daggerboard or rudder may lie more than 20 mm from its plane of symmetry.

5. Each rudder or daggerboard may only rotate around one axis. That axis shall be parallel to its plane of symmetry.

Rule 1 is easy to enforce. But, it would outlaw the Infusion. Rule 2 would allow daggerboard to be canted at any angle as long as the rudders were canted the same amount. Rule 3 should probably be in any combination of rules. Because I think boat tech is cool, I wouldn't mind having only rule 3 in place.

The current rule for reference:

The board cases, the daggerboards and the rudders shall be positioned in the centre plane of the hulls, and the under water parts of the boards and of the rudders shall be symmetrical.