Henra
At the limit of the envelope the margin can be as little as 30kts TAS from Vls to Mmo. MAch and GS have nothing whatsoever to do with it. The aircraft stalled. This is an aerodynamic event. How have you calculated your 'safe' mach numbers because they bear no relation to reality mach .68 could well be below minimum at high level and high weight.
I fail to see what the aircrafts inertia has to do with it. It may have a slight bearing on rate of stall recovery but the important info for stall recovery are aerodynamic. IAS, TAS AoA.
I say agian GS has nothing to do iwth it and only an idiot would use it to handle the aircraft when he has attitude and thrust available to him.