I think that the factor that most determines cabin position after impact is its position during fuselage hit and during rotor hit. So,after squeezing most of the RPM, maybe burying tail first to get large area into water, then hit rotors on the side (right for CW, and left for CCW so the tail don't emerse but to go in, and, whatever brakes now (blades, gearbox,...) at least cabin should be more or less in steady descent? After this, depending on the fuel quantity, thanks to vertical CofG it will probably go upside down (thanx to gearbox(es), engine(s), all up)...