Understand...Seems like possibly that the 657 may not be a good solution and you'll need to find another Linksys router that has this "NAT-Redirect" as this option seems to be a Linksys feature. D-Link has told me that VS works as intended however there could be specific port level conditions that your application uses and a process where VS may not be the answer where this Linksys feature works.
"Well, it works just fine when used as intended. I'm afraid to say is not possible, because we don't know exactly the requirements of the configuration he is trying to implement. If he has a special configuration that requires port level settings that are not standard, you will need to move into a corporate level gateway or firewall, but even at this level, it will be best to know exactly what is the port requirements. "
I think we've hit a feature barrier on what your asking the 657 to do and other than this, the 657 is probably working as intended.