Hi tophelios,
I think RPM high is a good idea, when hovering with high mass, not only for Cat A operation.
What happens, if an engine fails on you? YouŽll have an rpm drop before the other engine has a chance to serve you with increased power.
But it wonŽt be able to restore rpm to normal, as long as youŽre pulling power - which you will certainly do
.
The drop will not only affect the main rotor, making the bird more sluggish, it also effects the tailrotor/fenestron giving you less directional stability.
With rpm high selected you will still encounter an rpm drop - but from a higher startvalue leaving more rotor rpm when the other engine is up to full power thus giving you more time/rpm to play with to get out of the situation.
It is not forbidden to select RPM high at low speeds - so use it.
If you have the chance to have a ride in helisim, check it out - rpm high makes your life a lot easier, when an enginefailure hits you in the hover OGE.
Greetings Flying Bull