Well if they are playing fine from the backup channel you did everything right and you have a drive that can play backups. The only way to get backups to play through the official disc channel is via mod chip or DarkCrap. Read this part of the guide again:
Loading From Disc
New wii dvd drives will not read backup discs, no mater what. Does my wii load dvds? If it is new, probably not. Discs suck anyway, usbloading is much better. Disks must be loaded from a disk loader, like the neogamma channel installed on your wii. They will not work from the disk channel, unless you installed darkcorp. GC backups can be loaded from the disc channel without issue, if your drive reads burned dvds. Be sure to burn your dvds good and prooper. Burn them with ImgBurn, slowly 1-4x, set the "Layer Break" to 2084960 for dual layer games, on verbatim dvd -r. Other discs may work, but these are considered the best.