So,I finally figured out the usbhdd-install script is part of the larger dslinstall script which offers all the other options for hard disk installation. The minor device naming problem I found earlier in the week was due to the USB CF adapter on my laptop being /dev/sda, while the CF slot on the GCT is /dev/hda. I modified the sed command near the end of the script where it edits the syslinux.cfg file to resolve this minor quirk.
While this setup works well enough, it's strictly a 'LiveCD' type of install on the CF card. Any changes applied to the device aren't necessarily restored after a power-cycle. There's a restore option in the GRUB boot loader, but I figured out I'd need to perform an actual hard-disk install to the CF card to get a 'real' DSL system where things stick. So, I used the hard-disk install option which happily installed everything to the CF card. Except the GCT didn't like it. The BIOS just displayed the Gateway logo and sat there. Krap. I gotta figure out what the GCT BIOS is looking for boot block wise. It's happy with the IOSLINUX LiveCD type of thing, but I want a real Grub bootloader on there.
Anyone got any ideas or suggestions?