If we are talking about fatigue of the vertical stabilizer, irrespective of its construction being composite or conventional, has anyone ever noted the considerable vertical movement of the B757 horizontal stabilizer when take off power is applied and felt by this control surface. The more eagle eyed may have noted that the larger exhaust cone exit of the RB211 efflux causes considerable more movement to the stabilizer surface than the alternative engine CFM with a multi cone exit. Has Mr B noted this in the B757 fatigue test bed airframe?