In recent years, the folks at the Chicagoland RPM have presented a kit or minikit to registrants, allowing them to model a freight car not commercially available. The 2018 minikit was a truss-rod FGEX reefer, comprised of an Accurail carbody, a custom sheet of cast resin details, and custom decals.
Attached is my result -- built as a "layout model" (no museum-quality modeling here!) For the most part, I followed the Chicagoland instructions, with one exception. I have never had luck in scraping off cast-on ladders and grabs from a double-sheathed carbody. No matter how careful, I can't seem to avoid at least one gouge, and almost always end up with ghosts of the ladder rungs and grabs showing in the siding grooves. For this model, I replaced the siding on the ends and under the side ladders and grabs with #2040 Evergreen siding. I shimmed the replacement siding on the sides with .040"-thick styrene strip spacers. The replacement siding on the ends was slightly thinned, then laminated atop the original end siding.
A big thanks to Mike Skibbe, Frank Houdina, Tom Madden, and Ted Culotta, who made the kit possible.