PS 3 : Just a hint : when you load with ACE then save, then open your 757 aircraft in FSX to adjust whatever fuel you want, if you check the payload tab (fuel and payload menu), you would see that there is a slighly different total weight than what ACE was giving you, and this is because the pilots and attendants weights were added. I always remove all these weight as they belong in fact in the Operating Empty Weight of the aircraft (surely not Payload  ;D) For simplifications I would consider empty weight and operating empty weight similar.