From my experience, I believe a rudder has a phycological effect more than anything. If you think it works, it works. If you think it don't work, it don't. I have put rudders on a boat and the customer said, "That's great, it really helps". Then I've put the same rudder on the same brand and type of boat for another person and they say. "Waste of money, I can't tell any difference." So, I say, if you think a rudder helps use it and be happy. If you think it don't help, take it off and be happy. A rudder works from the wash of going through the water. When you are going docking speed, there is not enough wash to help. I definitely do not like one on a high speed boat. For instance, the Place rudder has part of the rudder in front of the pivot center of the rudder. This has a tendency to make the boat feel like a car tire driving on top of a sand ridge. They also give a boat tail lift upon deacceleration, which can be dangerous.
As far as the little cast ring on the bottom of your nozzle, it's most likely not even touching the water at speed as the boat lifts out of the water.
"Just an opinion"