[Skunkworks] Squid with tproxy option

Anyone on the list who has managed to have IP Spoofing on squid with tproxy? My environment; Ubuntu 9.04 server Kernel - 2.6.28-11-server iptables v1.4.3.2 squid-3.1.0.6 -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.