I have some G scale USA trains CF 4 bay hoppers:
http://www.usatrains.com/usatrains4bayhopper.html
Love the cars. Made well with excellent detailing. BUT......
the clearance underneath seems wrong? They'll hit anything that's sticking up even a fraction of an inch (1/16"??) on my trackwork. They even hit the switch frogs if the track isn't perfect. I have talked with others that simply remove the hatches on the bottom of the cars. I would prefer to know what's wrong. I see videos of them in real trains and the clearance seems much bigger in real life, even scaling it up.
I could simply raise the cars off the trucks with washers and then add shims to lower the couplers back down. Again, I'd prefer to get the car accurate and will do what's best to fix this. So I need to know how much clearance there is between the hopper's chute doors and the rails on the real cars.