This was the only image I found. If I understand it correct, I think you have a good solution.
Place the origin of the sections in their rotation points.
https://brickshelf.com/gallery/D-Dennis/...8483-1.jpg
There is a similar part, 86501, Container Fold-Out Race Track Case.
But that file is using subfiles, and is "locked", not possible to inline and change the shape of it. Maybe it could be changed?
Don't think we had the Flexible_Section solution back then.
Place the origin of the sections in their rotation points.
https://brickshelf.com/gallery/D-Dennis/...8483-1.jpg
There is a similar part, 86501, Container Fold-Out Race Track Case.
But that file is using subfiles, and is "locked", not possible to inline and change the shape of it. Maybe it could be changed?
Don't think we had the Flexible_Section solution back then.