It's silly. The former, an appendage has to resist the leverage that can be applied from all directions, from violent water, from debris, from grounding, the barn door rudder is on a full keel, it's simply a hinge, you can't apply that leverage, you don't have the same lever advantage.

It's like comparing full keels to fin keels for strength. One is like nailing a 2x4 flat into the floor, the other is like toe nailing the end of that 2x4 into the floor. The later(fin) you can kick right off(the longer it is, the easier it is to kick off), the formerI(full), you break your toes.

There's a huge difference in performance between the barn door and the spade/partial skeg hung rudder as there is for the fin vs full keel performance, and that's reason enough to sail the newer versions. They should simply be made as strong as they can be, and I would think it's prudent to design strength over performance, a bit, if the boat is designed to sail far away.

But to make a strength comparision of the two designs, is silly, they're not even in the same gallaxy.

This boat(CS 36) has been proven to be strong enough, I wouldn't take that trip with it though. But I wouldn't go in my own boat either, and it has a barn door rudder attached to a full keel.