One problem you may find on drop bottom Gons is that the doors will sag. In doing so they tilt the angle of the castings the chains connect to.
This results in an increase in the width from the hinge to the extremity of the casting and sometimes it is enough that the doors won't come down past the operating shaft.
I've seen all kinds of mayhem commited on the doors and fixtures by shippers trying to get them open so they can unload the cars.
Jim