I might beg to differ with the dog on that one, although i have no evidence to back it up. I would say, from the test results, it does appear that you would have three poorly performing reflectors.
The problem with small boats is that they easily disappear amidst the seas and rain squalls. Although, even ships will disappear in rain squalls. Unless you are steel or aluminum hulled, you are only going to "paint" a ship's radar screen sporadically. Anything you can do to enhance your radar return is advantageous. Multiple reflectors might do that, although additional inefficient ones may not be worth it. Certainly, if you were on a ketch, and could afix multiple high quality reflectors to each mast, I believe you'd increase the frequency of "painting" ship's radar. Regardless of type of reflector, excluding active units, a great many of your echos are going to be reflected either skyward or down into the sea. The boat and reflector are rarely aligned with the incoming radar beam sufficiently to give a good and consistent return. That is one of the reasons that radar watches must be actively held by a crew member, not relying on the "computer".
For multiple reflectors to work against each other they'd have to mounted in close proximity, thereby inducing some type of cancelling effect. As any motorist, dedicated to high speed travel, can tell you, this is very difficult to achieve.(g) Although, mounting them close to one another might induce false echos, that is to say, inaccurate ranging on board the radar equipped vessel.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.