The box is not specifically designed for the Protocraft Clouser coupler, since he wanted a more generic design. But I think I'll be able to come up with some way of mounting such a coupler in the box.
I have bought a six-pack of the coupler boxes and they arrived a few days ago, and in IRL they look like this:
The boxes are easily attached to the cars, using the original mounting screws and holes. They only need to be countersunk for the screws to not later interfere with the coupler shank. Here is one of the boxes test fitted on one of the cars.