I gave my opinions earlier.
There’s a very fine line between over confidence and actual ability, I’m not suggesting that the people who posted earlier are overconfident but it is possible. If you actually damaged the helicopter RRPM over speed for example practicing an auto, which is very easy to do in some helicopters, would you say something or keep quiet (assuming you don’t own the aircraft, but even if you do it needs to be reported)
As Parabellum said if you can afford your own machine you can afford to fly with an instructor once a month to practice a few autos. You’ll gain a lot more from it than practicing alone.
Practice alone at your own peril.