I seem to remember an ex AAC pilot telling me that the army decided to make a video of a Scout in VRS.
So two Scout's went to ten thousand feet, one the a/c to do the exercise and the other to film.
Apparently when the first a/c got in to fully developed VRS the other a/c couldn't keep up (or down?) so had to do the same and they both got down rather quickly, I'm sure over six thousand feet rate of descent was mentioned.
Can't tell you if it's true but stopped me going to far with demonstrations.