A 4 gig card might work better cause the 2 gig flash card is not going to be a full 2 gigs. Just like all hard drives it suffers from the same genius which plauges all writable media. It won't be a full 2 gigs. You might not even be able to fit osx on there at least maybe not Tiger. Even if you were able to it might choke with a swapfile. I say this cause my 2 gig Nano is only 1.7 gigs. I had a good install of Tiger running on my G4 Cube with only a 4 gig hdd, that would give a decent bit for the swapfile too.

my two cents
2.4gHz 15" MacBook Pro, 1.66gHz Core Duo Mac Mini, 2.5gHz G5 QUAD, 733mHz Quicksilver, 450mHz G4 Cube, 700mHz G3 iBook, 350mHz Sawtooth G4, 350mHz Revs. A and B B&W G3, 16mHz Powerbook 100, 8mHz Macitosh Classic.