Although the Sergent couplers are beautiful, I found them frustrating to use on my layout (which is more chest-level than look-down upon). I lived with them for almost 6 months, but I just couldn't get used to them, so the car's couplers have been reverted back to the HO-scale Walthers ProtoMax couplers.
Upgrading this car with the Sergent couplers wasn't trivial. I had glued the Walthers ProtoMax couplers in a custom arrangement to the car before when I built it. The coupler snapped off with a bit of wiggling of a jewelers screwdriver. However, for the Sergent couplers I like using the Kadee #802 coupler boxes, which are slightly wider than the center sill area. I had to clear that out, file everything smooth, and even cut away a bit of the center sill C-channel. There is no way to mount the coupler using the screws, so I used five-minute epoxy to attach the coupler to the car.
I was short one coupler (of the new design), so I used one of the old design Sergent couplers that I still had around. It was installed in the same manner. Later, when I weather the couplers, you probably won't be able to tell the difference, unless you know what to look for. Although the design is different, the two couplers work in the same manner.