I think that GEOS can be run from the stick, because the BIOS of the
computer will handle all read and write requests. There are two different
modes the stick can be accesed. As a super floppy or as a hard disk. First
try to boot from DOS only, because there are a lot of BIOS which won't let
starting from a USB stick. If it doesn't work, look for a new BIOS. Also
don't forget to put all often changed files to a RAM disk (swap file, cache
from the browser etc.) because the sticks have flash memory which can only
be written about 100'000 times before they can't be used anymore...