This is on a 46' Classic in S. Florida. New owner said according to PO it helps a lot. Don't know if the Prop Speed will work on the rudder and trim tabs though.
Seems to me it would have been easier to either enlarge both rudders, or at least add a fishtail to both.
Guy has a SD boat powered probably with big Cats, and he's wondering why it handles like garbage at 7 knot trawler speeds and in heavy following/quartering seas.
Helps what?
Three is just right.
Extra rudders help at slow speeds but not as much at higher speeds and add to drag.