Terminal Server Gateway 2008 - Is it possible to set up custom port?

Question

Hi guys,

On a terminal server gateway 2008 I need to change default 443 port to any custom port as a firewall itself already use 443 for its built-in web services and doesn't allow to set up port redirection for port 443.
I checked TS Gateway settings and found that it doesn't have Transport Settings tab.

Is there any other way to set up custom port on a terminal server gateway 2008?