http://www.dotan.com/article/.

The writer of the article discusses 100kg routine differences; but notes that in robust seas it could be 10 times that difference. I didn't write the article. I just saw it while looking at he the Ackerman Principle might apply to Multi rudder boats, including mono hulls. (Toeing-in or -out vs just vertical, etc)

Note these discussion are for a boat going forward, not aft; and it assumes that rudders haven't jumped their stops and are "brakes ".

Mark, what you sense at the helm isn't what is happening under the water. The existence of the bar does not make the stresses from one rudder transfer to the other rudder automatically. All that is supposed to be happening is the rudders are at the same angle. Example, which shouldn't happen on your cat, but illustrates the point: say one hull and rudder is substantially out of the water,, the bar would move the raised windward rudder, but there would be little stress on the raised windward.

If a cat has a bar to link the rudders, as opposed to a independent hydraulic system, then there are condition when the linkage bar may be In compression. Tension is easy. Compression of a long small section probably is a different matter.

A number of other cat designers have suggested that the stops and linkage system on the Alpha might be the issue. I don't design boats, let alone cats which are more complex than similar mono hulls.