Fixing Mekićevica's Rudder

Like many trailer-sailers, the Mantas have a rudder that can be lifted out of the water when they are not sailing. The drawback is that when sailing in choppy conditions the rudder swings a lot, which is unnerving and inefficient, as we were reminded last weekend.
So, I decided to do something to fix that: a piece of wood screwed to the wooden support of the rudder will prevent it from swinging.

It is not visible in the photo but inside there is a plastic bit that pushes against the rudder to keep it from swinging. The construction is fragile enough to be what breaks if we hit the bottom.