I did that change, i changed the folder from: ''gkoopa'' to ''gigakoopa'', and i changed the textures inside them with the changes aswell, but it still doesn't work. I have a PAL wii with some pal codeset. I don't know which version though, because i copied my friend's.
EDIT: I did what the above post said, i named the files: FitGKoopa00.pcs and FitGKoopa00.pac but Bowser still doesn't change to Giga Bowser. In fact, even without a costume he doesn't change O_O. Not that it matters a lot since i never play with Smash Ball, but i want to see the Giga Bowser texture xD.