You need the .rel file for any of the stages in question. You will also need the part of the stage that relates to the .rel file. As for the .rel file. It goes in the MODULE folder, and the stage part related to that .rel goes into the STAGES Folder.
Though I am no expert on stage swapping, so I would suggest asking somebody else who knows more about it than I do.
He said subspace stage not normal stages >.>