Dave,
Why do you conclude that X2 will operate in autorotation during cruise? I would have though the objective was in trim cruise. It just has full autorotational capability from this flight condition. It will be a compromise, but i would have thought the design optimised to suit 250ktas.
Any details on how variable Nr is achieved?
BTW, i've been thinking about puller vs pusher while generating a vortex panel model of a fan aerofoil. You could think of the puller as an additional vortex line generator (like the HIGE rotor image) so that the main rotor is operating in more favourable inflow over a pusher application. In a nutshell the puller wins out because a larger total area is ingesting air. Then again if the rotor is sized sufficiently this is less of an issue.