I originally posted this in the modeling forum, about eleven years ago. Since it took me a long time to find it again, I decided to save it here in the articles section, so that it will be easily retrievable. Hopefully, someone will find it useful.
Rather than use Kadees for this car, what I have done with mine is to take the USA coupler and file off a bit of the tang so it will fit through the coupler pocket. You have to do a bit of shimming, and then for security you can drill through the boxcar floor so you can through bolt the coupler, but it works great!. The coupler comes out the pocket, just like it is supposed to do, and you don't have to buy any Kadees.
What this method does is prevent the butchering of the car so that body mount couplers can be added. I butchered three of my collection, and hated doing it because it ruined the look of the car. This preserves the model intact, with body mounts, and you don't have to buy Kadees for it. It will easilly go around a 10 foot diameter (5 ft radius) curve, without problem, both being pulled or pushed. I decided to place the pivot of the coupler closer to the end of the car, so that I could get to use a smaller radius curve, but, as you can see, the coupler tang sticks out a bit. I'll leave it for you to decide. Just remember, the knuckle will stick out an unprototypical distance.
The above coupler is mounted close to the wall, allowing for a wider swing. I've used it successfully on 6 ft diameter (3 ft radius) curves. The downside is that it makes for an unprototypical gap between cars. The car below has the coupler mounted at a more prototypical distance. It will easily do 10 ft diameter curves, but not a 6 footer.
The above coupler is set for a more prototypical gap. I've had no problems with it on 10 ft diameter (5 ft radius) curves. By removing a little bit of the plastic on the coupler box, you can get a wider swing, enabling smaller curves. Be careful that you don't remove too much. I've run several cars back to back on the same ten foot diameter curves without problem.
The white box tube is from Plastruct, and it just .250 inches. Looking at it again, I would add a .010 shim (or two) to the box, and see how that worked
Some folks have a problem with the knuckle failing (vibrating open) under the stress of a long train. I've found that the solution is to give the knuckle a coat of "Rust" or "Brown Camo" paint. The added friction of the paint seems to be enough to prevent the knuckle opening under the strain of 20 or so cars with metal wheels being pulled up a 4% grade. Your mileage may vary. Dave Goodson and Ric Golding gave me the tip. If the paint starts to come off, and the couplers open again, just give them another shot (not too much) of paint.
It matches the Kadee height gauge very closely, close enough that I've had no problems with uncoupling. And, it looks GREAT!