Nevertheless it's operating at a negative lift coefficient and that lift force is communicated into the model and hence to the wing which then has to lift harder and put more energy into the downwash so that the tail can surf on it if that effect is indeed taking place. Either way you can't get something for nothing.

PS: I see that your source site agrees with Race's thoughts. At least the guy shows it as an add on load and in a much smaller size as is befitting of it's effect.