The Dotans might have changed since I tested them, but back then there were two rudder positions -- full up and full down.
That simply will not work in our area and for distance races or races off and on beach, i.e. Tybee 500, Steeplechase, etc.
You need a rudder system that goes up only as deep as the water is. If it pops all the way up, you have NO steering. Scary in the surf.

Also the plastic heads were quite flexible and I saw a lot of yawing, allowing the blade to not be stiff.

Again, this was tests we ran when they first came out. They may have made many improvements since then. Hope so.
Rick