Hi Ben,
I don't know if you have allready solved your problem. I had neary the same and here's how I've got through:
Just create an empty folder under your 'Document_root', let's say HFS. Then put in it the .htaccess file with the statements in the attached file.
Notes:
* Only lines 1,8,9 are required. Other lines are to avoid redirecting these folders if found under Document_root.
* In my case, I'm not changing the Server's IP adress, so I this will work for you. I think that it depend on your rooter.
When I tried this way, it was ok in my LAN, but not from the outside.
* Another way to test is VirtualHost (see Apache Document about this).

Good luck
Horacio.