Originally Posted by
CE-HAM
It's not easy. Moving wings or control surfaces forward and aft has many more consequences than moving "dead weight" as a door mechanism. For pax ops, the wing was/is in its optimum position. Now Airbus wanted to add some weight (the door) and it was better to put it aft of the wings and not forward. Thus the aircraft can be trimmed less nose-heavy and drag is reduced.
Now you've lost me completely, I'm afraid.
If we agree that the 4,500 A320s built to date had their wing correctly positioned(!), then adding the additional weight of a cargo door either forward or aft of the wing would require compensating changes in the weight distribution on the other side of the wing in order to maintain the CofG in an acceptable range relative to MAC.
That's no different to what happened, for example, when they stretched the A320 into the A321 by inserting fuselage plugs both forward and aft of the wing - in fact the forward plug is around 50% longer than the aft one.
So it's hard to see how there would be any specific aerodynamic advantages resulting from putting an A320 cargo door aft, rather than forward of the wing.