You could change the boot.img size perhaps? Try this:

dd if=/dev/zero of=boot2.img bs=1k count=1600
mkdosfs boot2.img

Then just copy everything from boot.img to boot2.img (with cp -dpR * perhaps).
You should be able to edit the help menu and boot message without changing the filesize too much - just use nano or vi or something to edit the f2 file.