Question to Mark:  I understand how to load the passengers/cargo using the ACE. That tells me the total payload weight. Then I can calculate the required amount of fuel and see the fuel weight in the FSX fuel/payload window. However for operating purposes, I need the aircraft gross weight, i.e. empty weight + payload + fuel weight. I can calculate the GW separately by hand, but this will not be the same number as in the FSX fuel/payload window, which only shows the crew weight for payload.  How do I know that the FSX flight dynamics calculations use the  real GW and not the one shown in the FSX fuel/payload window?