I had the pleasure of working briefly with Mr. Joe Vida (high-time SR-71 RSO) at the B-2 CTF in the 90's, Joe had some neat stories but always left things open for interpretation, could only say so much. Also worked with Bill "Flaps" Flanagan, former SR RSO.If you take a look at the cockpit mach indicator for the A-12, YF-12 and SR-71, you will see dashes from m3.5 to m4.0, interesting, just an observation.