I think that the Mcrit is a figure that you never need to carry an airplane, because it varies witha a lot of factos. The definition of it you have more that one time in this topic, and says that the Mcrit is the the mach number at wich any part of the aircraft first meet mach 1, so it depends on the angle of attack, bank, gust, and it could be on the wing surface or even the fuselage, so the only parameters regarding mach numbers are the MMO, adverse weather or turbulence Mach target, andthe buffet onset for given weight and FL, in airplanes with efis you can find it so easy.