I don't know about 2 memory cards, but I do know you need a freeloader.
Normally... things like this don't require a memory card at all... just loads into memory and then you swap the discs.
I wish I could find the freeloaders..... I don't know how to get them... as I have been trying to bring some in. there are some great Gamecube import shooters (Shmups).
BV :hat