The Zp is important for all helicopter, but for short powered helicopters as R22 is essential....Many young pilot ( or not) forget the difference between hovering IGE and OGE. The difference is a rotor diameter altitude and 7 percent of power...
If due to the load and Zp, you are full power for the hovering and take off , you can't hovering OGE. that's all !
After a while, when you have burned some fuel, you earn some percent...BUT you need to burn minimum 7 per cent of your load to perform a hoveing OGE.
Then, depend of the OAT and pressure....Little be more, little be less
If not, and you try to hovering Out Ground effect, The FAA name this mistake "SWP" Settling with power...