You only really need a .rel if the stage you're replacing isn't the one your new stage was made for. Since you want a stage based on Pirate Ship to go over Rainbow Cruise, you need a rel. Keep in mind that unless you change the name and portraits in common5.pac with BrawlBox, it'll still
look like Rainbow Cruise on the stage select screen, although the stage will load as Clock Tower when you pick it.
You're welcome! If you need any more help with anything, you can always PM me.
You know, if we can have a Castlevania stage, I wonder what other series not in Brawl would have some good stages. Can anyone think of anything? Maybe one of the older Final Fantasies that were made for Nintendo systems. Temple of Fiends / Chaos Shrine?