Pablo,
You fly a 25 Year Old 747 whos' engines are tilted towards the ground at high attitudes. I fly 737s between 1 and 20 years old which do the same.
All the Stick Shaker and Stall Speed graphs I have in my Boeing FCTM specify Idle Thrust, as stall speed is different with thrust applied. Idle thrust stall speed varies with weight. If vectored thrust (By the deck angle, not adjustable nozzels) is supporting some of the weight, it has the same effect as a lighter aeroplane= lower stall speed.