Interesting kitbash!

I missed the Freytag article/pic. When/where was this?

I'm pretty sure I can see how the joins were made so I could easily craft one (or more) of my own. Love the outside bracing in the bottom photo. What did you make the deck out of? It almost looks like the underside of a 2-bay hopper with a new frame. More importantly, how LONG are these cars (in inches, not scale)?

How the car was built.

The deck was built from .060 styrene sheet. I cut it 7 inches long and as wide as the cars. I also cut a piece of .060 styrene to fit inside the cars on the bottom where the original frame went. If I didn't do this there would have been a very noticeable gap between the belly of the car and the new deck,  The the frame is a  .080 square rod cut to length but allow enough room for the couplers on the end. The side sills are .020 x .080 cut 7 inches long. The hoppers door was cut from a Roundhouse 3 bay hoppers, and had each one had to be sanded to fit.

Only time I have every seen pictures of this car was from pictures I don't think there ever was an article about these cars or if this car even showed up in pictures that was published.  

Any more questions just ask.