@d3co: The game is pretty much identical to the original from Japan. Only the language is different. So the German version of Pokemon Platinum would still be needing a 1mb savefile size if you don't want anything weird happening to your savegame.
@clydefrosch: I don't know if it will help you but you should take a look at the sticky about YSMenu. I believe it's in the R4 forum but so far I've read that YSMenu can be used on several flash cards. YSMenu does support 1 mb savefiles if you add a few files to the kernel.