netfilter with transparent squid

does anyone know how to setup a netfilter-firewall with transparent squid ? there is a document called "transparent proxy with linux and squid mini-howto"; sure it works, but only when the default policies are set to accept; for higher security my default policies are set to drop and the transparent answer my requests; does anyone have a similar szenario that works ? are there some samples or useful hints avaliable ? thx alex