The long edge isn't what is being measured in a sizer, it can be 48 inches long and still fit into the machine. It's the other two dimensions that have to fit into the cut out.

the 24 or 20 or 22 or whatever only comes into play if they have you insert it in one of those "must fit in this box" things, and unless it's obviously huge I don't think that will be an issue. The issue, I think, is if it fits wheels first in the overhead.