I'm still unsure as to whether it's really necessary to partition the card at all. Mount an ext2 partition using "mount -o loop" - requires the scratchbox mount command rather than the built in one. Use mkfs on a linux box to create the partition files (dd if=/dev/zero ... to make the empty files) then gzip and copy to mmc, unzip and mount.

It may be slightly less efficient, but makes changing the size of the (pseudo) partition much easier, or just add extra partition files as needed.