Providing external url for the fqdn for webfeed returns error in eventlog that shows internal url is being used - how to change to the external url?

I've got my Rdweb accessible on both my internal and external network by using split dns locally to resolve the external url (remote.domain.com/rdweb) to resolve and everything works fine. However users don't want to use the rdweb interface (as it is slower than just clicking on a rdp shortcut.

Following the notes at http://social.technet.microsoft.com/wiki/contents/articles/14488.distribution-of-remote-apps-and-desktops-in-windows-server-2012.aspx - I've tried to set up the webfeed on a Win7+ machine but when I enter the external url that is protected by an SSL cert the eventlog shows that the internal address is being used and it doesn't match the certificate. - "There is a problem with this connection's security certificate.
The remote computer cannot be authenticated due to problems with its security certificate.                        
Security certificate problems might indicate an attempt to fool you or intercept data you send to the remote computer.                       
Windows cannot continue setting up this connection. Contact your workplace administrator for assistance.                         
Connection name:

Connection URL: https://internalservername/rdweb/feed/webfeed.aspx

How do I set the servers to use the external address rather than the internal one - i'm assuming it's similar to exchange's
Set-webservicesvirtualdirectory command but I can't find the equivalent command documented anywhere.

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