I updated the setting above by removing the double slash after 'Feed' and the error message disappeared. I tried to find out what the double slashes mean, but I couldn't find anything in the SS docs or forum. I saw it being used in the sapphire/_config.php file and it looks like a delimiter between the url segment and the params so I copied the format.
Anybody have explanation as to what the double slashes mean?
The double slashes define a shift point in the URL - basically everything before the slashes is shifted off, and the stuff after it is passed to the actual controller to handle as it sees fit. This would have meant that your controller was passed everything after "Feed" to handle. Since it then didn't have a matching rule defined in $url_handlers, it errored out.