uncompressed audio in redcard

[Neopolss]

I recently got ahold of kalisto rip version of redcard and wanted to downsize it to work on my no solder, however when the iso is extracted, the files come to over 2 gig! The audio files are compressed within the iso, but my question is this. Once i have dummied the pss files and set them to go, how can i create an iso and compress those audio files back to the size they were? Any ideas?