the problem is that for load GSX sets only one cargo container per cargo door
No, it doesn't.
As explained on the GSX manual, the number of wagons (and so the number of cargo containers) is calculated from the estimated number of passengers on board, which is calculated by dividing the total weight of all loading stations for that airplane by 220 lbs. so, regardless if the airplane is passenger or cargo, as long as you have your stations loaded, it should come up with an estimated number of passengers that would have several cargo containers to be displayed.
If you only see one container, which is the minimum, it means GSX thinks you have 0 passengers on board but, since they are calculated from the total station weight (regardless if the airplane is supposed to have 0 passengers, as a cargo), the only possible explanation for this, is that you haven't loaded your airplane.
As a reference, with a large airplane like the 777, you should see 5 cargo wagons.
Yes, this is not realistic, because a 777 can load much more ULDs but, as explained many times on the forum too, *everything* in GSX is scaled down to reality, to make the process less boring. Same as you won't see 400 bags loaded on a 747, you won't see 40 ULDs loaded on a large airplane so, everything is RELATED to the actual airplane capacity, but scaled back in comparison to reality, otherwise you would be staring at the screen for too much time, to see the loading taking place, if it all timings were 1:1 true to reality.
