Open the MGS ISOs with a hex editor of your choice, search for the following byte sequence...
7F461E70: 72666C62 744F0000 3F800000 00000000
7F461E80: 43300000 80000000 49A00000 49A80000
7F461E90: 42480000 40000000 00000000 3F800000
7F461EA0: 00000000 00000000
3F800000 3F955555
7F461EB0: BF800000 45000000 45800000 4B7FF000
7F461EC0: 3D4CCCCD 00000000 43300000 80000000
7F461ED0: 00000000 00000000 43300000 80000000
and change the marked hex value from 3F800000 to 3F400000.
7F461E70: 72666C62 744F0000 3F800000 00000000
7F461E80: 43300000 80000000 49A00000 49A80000
7F461E90: 42480000 40000000 00000000 3F800000
7F461EA0: 00000000 00000000
3F400000 3F955555
7F461EB0: BF800000 45000000 45800000 4B7FF000
7F461EC0: 3D4CCCCD 00000000 43300000 80000000
7F461ED0: 00000000 00000000 43300000 80000000