There's an automatic formatting function in the overobuntu builder that will automatically create the correct partitions (and partition sizes) for any size SD card. You can download the overobuntu builder by going to gitorious.com/overobuntu, or by running the following from your terminal:
git clone git://gitorious.org/overobuntu/overobuntu_builder.git
Run overobuntu, with the following parameters:
replacing /dev/mmcblk with your device. DO NOT use mmcblkp1, etc, as these refer to a specific partition rather than the card device itself. Make sure you use the base card device (ie: /dev/mmcblk on my machine).
Once Overobuntu has started, click on the "Card Options" menu, and click on "Format SD Card". This will automatically correctly format any sized SD card to boot on the Gumstix Overo, with a FAT partition for the boot files and the remainder partitioned for the root file system.
RAD Software Systems
We're RAD software systems, a software development and engineering firm that specializes in Rapid Application Development. Our team of software engineers uses state of the art agile methods, ensuring our clients deliver on time and on budget.