I got a Shapeways package today with my first try at a True-Scale coupler pocket. The design is pretty simple. I'm using the long shank coupler with the screw through the coupler hole and a floating wedge at the springs. There is no provision for centering, and I went as narrow as I could for a one piece design.
The design works as intended although it does need some clean up to do so. He it is on an Atlas PS-1.
There are a couple big downsides however. First, there's too much coupler swing, but that could be addressed. More importantly, using the coupler hole for the mounting screw has two big issues. First, it's a poor place to have to tighten down a screw without some sort of bushing. It just squeezes the coupler halves together effecting operation. Second, in order for the the long shank coupler to stick out form the body a prototypical distance, it needs to have a hole drilled about .0828" back from the sill. But many models already have some sort of hole designed into the floor in that area so it can be difficult to drill a clean hole. In the CNW example, the coupler and pocket should actually extend out farther than they do to be prototypical but the factory hole prevents doing this so I just used what was there.
Rev B is already in the works and should go to the printer in the next couple days after I make some adjustments based on these samples. THis will be a two piece design with a lid and hopefully a more universal way to mount it at the correct depth.