I have some familiarity with ROM hacking on the PSX. I know that if you were to replace a file in a PSX ISO, it involves the use of CDmage, and the new file needs to be exactly the same size as the old one. If not, the image won't load (i.e., teh gaem is broken).
But what if the new file is larger? How would one go about replacing files in the ISO with larger files without breaking the game?