Mitch and Tiffany, Sounds like you are on the right track with the size you propose. It all depends on the size of your birds or the size you hope to progress them. Just make sure they have room to sit and not mess up their tail. Some folks will offer a longer length for males in many breeds. And you might be able to get by with a slimer version for carrying AMs especially females. These are sizes offered by a couple builders, and if you get in a routine and offer them for sale, please let me know.........
LF boxes in 2 sizes - 16in wide, 16in tall and 24in long, and 16in wide, 24in tall and 24in long.
Some of the folks are using plastic totes now for carryy boxes, they are cheap, light, and they can be stacked inside each other for the off season.