Helicopter stability?

[helisphere]

Possibly it is slightly below his feet but this would still be well above the thrust plane. The empty weight is about 370 lb and the engines are above the rotors.

 

[helisphere]

Here is a small stable coax heli that has been modified to fly inverted. Looks pretty stable.

https://www.youtube.com/watch?v=l1azqZhWsrU