I am not confident from the pictures that this is the same thing but Prone Paddle boards have had a 2 in 1 steering for a long time. They use the batten steering etc but it has worked for them for ages.
The extremely rough diagram below shows how it works.
The fixed fin at the front holds the board in a line and directional, the rear section of the fin is free and controlled by the batten or steering system which steers the board. This would stop the board under rudder and the board still sliding sideways thing you get in the surf etc.
To me it makes a whole lot of sense.
I've had a fin and rudder system on my DC14 for years now. It was originally designed this way as a backup system in case of a rudder system failure on a long paddle. There was a lot of debate going on at the time about racing with/without rudders systems so I decided to have both options available. It was a great idea at the time but I have never had to use it.
We also fiddled around for a while with a combined fin/rudder system like the one CMC describes.
This deep looks really nice and its local, which a good thing in my book
