I made a patch for the retail USA UMD. I tested a few battles, and I did not notice any slow down. I tested Gaffgarion and Agrias's sword skills, haste, blizzaga, and some summons.
Original USA ISO
Size: 418,873,344 bytes
CRC32: 0D6A3D9F
MD5: 18D1169CEFED2D5ED77A599694F2F871
After patch
Size: 418,873,344 bytes
CRC32: 8762459E
MD5: 6690A74151890EE1DB2F2AA0617A723D
Original USA ISO
Size: 418,873,344 bytes
CRC32: 0D6A3D9F
MD5: 18D1169CEFED2D5ED77A599694F2F871
After patch
Size: 418,873,344 bytes
CRC32: 8762459E
MD5: 6690A74151890EE1DB2F2AA0617A723D