Could X2 stay aloft at high speed on slowed down main rotor lift alone......that is the question.
I would expect it would stay aloft on main rotor lift alone, after all what else is keeping it aloft in the first place? If the thrust went away, surely it would decellerate though.
I guess I am in the camp that thinks the X2 fits this definition exactly:
Section 9 of the group's Sporting Code for rotorcraft, available on the NAA website, says a helicopter is a "rotorcraft which, in flight, derives substantially the whole of its lift from a power-driven rotor system whose axis (axes) is (are) fixed and substantially perpendicular to the longitudinal axis of the rotorcraft."
-- IFMU