Just-nick
Sorry but you still won't "know" anything. The results you get going outside of the simulation limits may well have no connection to what would really happen. The models may extrapolate in a linear direction but the aircraft response could be very non-linear, or reverse direction. An aircraft is required to be directionally stable at Mmo but it is acceptable to be mildly directionally unstable at higher speeds. I suspect this is not modeled in the simulator so if you were to go and do rudder inputs above Mmo you may well "know" an incorrect result.