I suggested in the other post the combined use of winrar+par for archiving and sharing gamecube discs.
Here is a try: you need packps2, winrar (I used v3.71) and quickpar.
Games tested are 3 wide avaible:
Legend of Zelda, The - The Wind Waker (U) ---> size: 1163204188 crc32: 96D006C2
Metroid Prime (U) (v1.00) ---> size: 1234752507 crc32: 977C94A3
Star Fox Adventures (U) ---> size: 1181050994 crc32: E6EB4228
Do as follow:
1) Rename disc as in DB (uncompressed and make a backup)
2) Rename disc to .iso and start compressing it with packps2 until a .7z file is created in the same directory.
3) Now close prompt with "x" and you'll see .7z will be deleted, but you iso date has been set to 01/01/1980
4) Rename the disc to .gcm
5) Compress disc with winrar standard setting (simply righr click on file and winrar ---> add to "file_name.rar")
6) Repeat point 1-5 if you want to test it on all 3 discs.
7) Once compressed check with these pars how many blocks you need and report it here.