I was thinking there may be a way to NOT auto-snap-grab the ledge during the up-b recovery-- maybe by pressing down or L or something before passing the ledge. And then I think I saw it actually happen in this video. Occurs at 1:25 with Marth's up-b. He's definitely close enough that it should ledgesnap, but instead he goes right on through and onto the stage. I think this should be tested for sure.
http://youtube.com/watch?v=bomqTRx9XvA
http://youtube.com/watch?v=bomqTRx9XvA