If I did not understand you wrong, if you delete port 80 from redirected ports of WebShield, you will disable the transparency of the WebShield proxy but you should configure your browser to use:
proxy server name: localhost
proxy server port: 12080
If you do not setup your browser, I think you will 'disable' WebShield.
Sorry if I'm misunderstanding your posts. Please, correct me if I'm wrong.