Hi Sean, very good info there...  I still have to go/read all of this data you put here, but it triggers the question IMHO as how detailed and exact you want to use / hope to use FSX for simming. For me it's OK even if the trust figures, engine model, CG calc. (as long as it does not impact the flying model) etc... lack 100% accuracy. Doesn't spoil my fun as much as the ability to fill the tanks and load almost 100% payload trough ACE as I know THIS is FAR from reality. Now this was bugging me, and so I made the tables above when I relaised the ACE did not a good job at load calcs. It is meant to at least let you load you aircraft to the max payload as found in the general Boeing docs and see how far you could go... anyway thanks for your info.