Your best to use a true Magi Gate SONY Memory card 8 meg, for FMCB.
You can install it to bigger cards but risk the chance of data corruption on later save games as the exploit "Breaks" the file system. Avoid using MADCATS 3rd party MC's - Complete junk
I have a 64meg memory card in SLOT 1 and a Sony 8meg in SLOT2 with FMCB Installed.
90% Of PS2 games require only SLOT 1 to be used when saving games, so makes sense to use SLOT 2 to boot FMCB
Also works Via Multi-Tap in slot "A"EDIT
Note that NOT ALL GAMES will be compatible with 33/64meg MC's and eather
a, Refuse to Load whilst card is plugged in. Or
b, Take an age to access the card (Vice City)
I keep a spare 8meg card for these "Problem" Games