One has to watch for some fiddling of reported weights from some shippers. Some packed their containers at their facility but of course, our Air Freight people weighed each one as it was received, or at least so they assured us they did so. When a loader-lifter refuses to raise two LD-3's, its hydraulics screaming in protest, one gets suspicious. Each had a weight of 3200-lbs chalked on it as testimony that our people had weighed it.
Fortunately the Chief Pilot at JFK was walking the ramp with me and he insisted they take the two back to air-freight for "reweighing". Each one of those two LD-3 exceeded 11,000-lbs, somewhat in excess of the 3500-lb limit. They were packed with flat sheets of aluminum stamping going to a factory in Puerto Rico for bending and assembly into TV sets. Our local Air Freight department suffered a change in local management as a result.
We had some B747-100's that had strain gauges on the gear feeding a built-in W&B system. They never worked very well and ended being deactivated.