DHCP settings in Internet Sharing

My G5 connects to the LAN & Internet via Airport. I have a G3 and a PC next to me which don't have airport cards. I have setup a hub, connected to my G5's ethernet port and shared my airport connection. Here's the problem; I'm on a 10.0.2 subnet and the main wired LAN is 10.0.1 (bridged by the airport base-station). The Internet sharing DHCP service assigns addresses in the 192.168.2 subnetfrom my G5. Whilst this works for accessing the Internet, I can't access these two devices from the 10.0.x subnets (apart from the issuing G5) for filesharing . Does anyone know how I can force the DHCP element of Internet Sharing to assign a 10.0.3 subnet address? I really need to solve this as my partner and I use the same mac, the G3, as an iTunes server