I'm still not sure that Hachiouji-shi actually understands what you have been saying, OS?
H-S - Mcrit is when the FIRST shockwave forms on an AIRCRAFT - on any part. It has nothing to do with Mach buffet or MMo, climb or cruise speeds.
For Old Smokey, my piece of the jigsaw is that I STILL believe the cockpit roof on a 737 is where Mcrit 'happens'