Yeah, that sounds good Rolf, there's plenty of extra room inside the castings and additional thickness and strength would be welcome. I'm sure this is a major stress point for the rudders, as they attempt to bend sideways under load.
I'm also not so pleased with the hollow rudders and water intrusion. My thought is to fill that little hole down low, as well as the 2 I created for the hold down/lift lines, then maybe drill a small hole on the top of the rudder to minimize the amount of water that gets in. Has anyone completely sealed the rudders? I don't leave mine on the boat when stored, they might sit in the sun a few hours between sessions at most.

Dave