firestarter for ICS (Internet Connection Sharing)

[THUFIR HAWAT]

I'm going by <http://www.fs-security.com/docs/connection-sharing.php>
to set up ICS.

in my setup, I use a wireless network adapter to connect wirelessly to
a router.  The wi-fi NIC connects to the computer named arrakis. 
Arrakis in turn connects to a hub, which connects to the computer
named caladan.  There are only two computers, it's somewhat similar to
the diagram showing ICS for two computers.

The "external" NIC for arrakis is connected to wi-fi NIC.  The
internal NIC for arrakis connects to the hub.  I believe that this
creates a double-NAT situation,which isn't good.  I've yet to find a
way around this, but am searching.

Can firestarter be used to setup ICS in this situation?  In the
diagram showing two computers only, which is what I have, the external
NIC, eth0, is connecting directly to the internet.  In my case there's
a wireless connection to a router, which then connects to the
internet, so it's not quite matching the diagram.

thanks,

Thufir