The "duck" is a Diesel Duck mon! A not-very-pretty but said to have the ability to grow on ya, George Buhler design. I guess you'd have to be a Trawler Crawler to fathom these depths...
Now, about the duck's flopper stoppers (paravane stabilizers): The article mentioned something about the Aussie system, where the fish is not deployed very deep, like at about the vessel's draft level. And, according to the writer, because of the shallow deployment, the fish don't fly out of the water and attack the boat. ?!? So for the life of me I can not figure out how with that kind of short wire on the fish you would not end up with the opposite...how can you put the arm out far enough to have leverage and not end up with a lot of vertical distance gained during rolls...I guess close in may work for a really light boat?
Actually, the whole topic is an oxymoron, because if arm and wire lengths are properly designed, then old Capt. Beeby's system works just fine. People and boats get hurt when the boys just decide to build something one afternoon and throw together some pipe and cable on a
plan-as-you-go basis
Who knows, the whole thing could be one of those misterious things you read in boating magazines, that could only exist in boating magazines...
Trouty, you'll have to go to a commercial fishboat harbor to see paravanes. I don't think you'll see them too often on pleasurecraft, except maybe the real salty ones, like Nordhavn.