The fixed keel boats that most people race are faster than our boats. (the J boats come to mind)
They don't seem to suffer too much from not being able to raise their keels.
ON the other hand, their keels are much larger and provide more "lift" than ours do.
That's how they point so well.
The keel in that picture looks like it has more area than a standard Mac daggerboard.
I would think it would make the boat point better. If you are racing that might help you but don't you have to notify the race committee of improvements? They would adjust your PHRF I'm sure.
In my area, we have a lot of shallow water and I wouldn't want that under my boat.