Using non-web server publishing rule to publish web server

Hi

I've have to do this because of a problem with the way TMG passes authentication details to the website using the standard website publish rule. All I want tmg to do is publish the site's logon page however as soon as TMG realises the site requires authentication it steps in and passes the username/password to the site in a manner it doesn't understand, even on basic authentication. With all authentication off I just get a 403 URL denied error.

The site is running on 8080 and all I've done is point this traffic to the web server. Seems to work fine however there must be catch, is this safe?

Thanks

Rhys