Hi Gizmo,
it is not possible to hide something to the user... it was possible previously but for security reason, browser display the real URL...
The only ports not displayed by the browser are default of the requested protocol:
If you want to hide port, the reverse proxy must listen on the default port and rewrite host header with port number, and sometimes rewrite responses
But, the better solution is to define in the back end server the proxy hostname and port.
ex, in tomcat, you can define the following parameters...
Look at your application admin guide if it support this feature.