I have two of those kits in my stash, both in the green Wright Trak boxes. I might take some pictures for you to look over.
I think I would test the waters much like you did with the 12 post and see what comes about. I know one of my kits will
get one of Tony Sissons’s replacement doors. Which might be an option in updating the kit as well.
This style door:
I can say anything you do in the double door version, I will get two kits.
Don’t forget about the WS RPM:
A model of the long-awaited 12-post PS 5277 cf boxcar is close at hand. Pullman-Standard manufactured these exclusively for Southern Railway and the original Norfolk Southern starting in early 1973. Models have never been offered. Design is about 80% finished …only a few details, the brake system and final review remain. Patterns will be printed in-house, thus eliminating quality issues, escalating prices and shipping delays experienced with SLA suppliers.
Contact me off-list to ask questions, place an order, etc. Depending on market response to these kits, other cars based on this design will be produced, including the waffle side version in single and double-door styles.