Deefer,
Please excuse me as it has been 8 years since I moved off the classic to the electric variant .... so, for the alzheimer's version:
The speed spread between cruise and MERS was small at altitude, perhaps 6 kts....not stall. MERS (not a term used as much anymore so excuse me if I am telling you how to suck eggs) is a high (er ) drag condition whereby you needed to descend to get the speed back.
The old girl was temperature sensitive. With MTOW 377.8 and ISA + 16 or above you would struggle to get to Fl280 before most FIR boundaries. As such you were always doing calcs in your head on the climb working out whether the flt plan ISA dev was accurate.
Pushing alt at a heavy wt is dumb in any a/c, but particularly dumb in a classic and it is this condition that would get you close to what you are describing.
6 kts however does come to mind on a hvy wt departure as the diff between the flaps up speed and the over speed (275 rings a bell) as the leading edges retracted (groups 1 and 4 from memory) and it took a deft hand to keep it finely balanced.
Great a/c, truely loved my time on her.