Cleartunnel and non ISA Upstream

I have, in my LAB, been struggeling with getting Cleartunnel working. I have come to the conclusion that it does not work in a NON ISA Upstream Proxy setup.

The setup beeing :

Internal Network->ISA 2006 Enterprise with Cleartunnel Add-IN->Upstream Proxy server->Internet

Cleartunnel can only work in Full Bridge mode if it is the edge or downstream server to another ISA server.

At the present, there is no working solution, other than upstreaming to another ISA server or finding another solution in your external dmz...

Thought I might let you know..