Yes, they can be unevenly loaded while turning. Boats with crossbar linkages, like the Alpha 42, often have it set with a differential connection between their rudders (called an Ackerman angle) so their rudders do not have the same attitude during a turn - each one is turning to the radius it needs.

Besides, the normal steering conditions are nothing like double fault mogul fields - do you really think catamarans are continually steering short, sharp turns and jumping left and right off of wave faces all over the ocean? Here is a bit of real experience - they don't steer any differently than a monohull. They take very little rudder movement to make small and infrequent adjustments while keeping a straight line through all seas. Downwind, they require almost no rudder at all because they track like a train on rails.

But I don't understand why you are making such a point about this? Are you still convinced the rudder surface area is too small? That is nonsense because every catamaran built has similar rudder area and none of your supposed problems are occurring. And these rudders are designed by very well-educated and experienced people. Certainly, if the area was too small, someone would have noticed that in the past 30yrs of producing tens of thousands of 35-80' boats around the world?

And the reports from the Alpha 42 never mention anything about having difficulties steering or controlling the boat before it was damaged. If the rudders were "too small", wouldn't they have less chance of being damaged because the loads would be less? Wouldn't "too small" work in favor of the smaller rudder stock?

Mark