Hi Air Clues. I worked for a 747 operator that had to follow UK CAA air test requirements. My recollection is that Boeing were horrified to find out (rather late in the day) that airlines were stalling 747's and particularly were concerned about the loads on the horizontal tail due to the buffeting. IIRC, once Boeing found out people were stalling the 747 they required a Severe Turbulence Inspection of the tail after a full stall. After this the CAA changed the requirement to check stick shaker activation speed only.