Coyote gets my vote as the best solution so far. The tight descending turn gets it on the back of the curve. I would be a little careful still of using the throttle. What you are doing is removing the N2 governor from the game by resetting the Max N1 stop. I think this would complicate things more than would be benefitted from it.
Put everything you have in the left rear corner so to speak. It was standard practice moons ago in a H500 to get the things down in a narrow vertical space. Huge rates of descent can be seen with very little airspeed. From the ground it looks like an aeroplane in a spin and probably follows a similar path.
Once you get it near the ground roll out and close the throttle to idle and wait. The tail rotor still works of course so at least you would be able to keep it straight for a while. With this pitch setting though RRPM is going to vanish very quickly and you would hope to be close to the ground before it starts to rotate. Contrary to the simplistic view of some there is friction in the drivetrain.
Whichever way you slice it - nasty.
Again moons ago it was possible to get a H500 to spin around a point with 90 degrees of yaw to the extent that it would look like it was 70 degrees nose down and looked like an aircraft in a spin yet it was not descending, in fact if you were good you could get it to climb like this. The limiting factor was available power. It looked really strange and on reflection probably really stupid.
Back in the days of Young, Dumb and F............