I would contact the Nikonian Pro shop and ask about TB-30 compatibility with your Mountaineer GT3541. It should be compatable, as far as I know there has not been any changes to the Mountaineer GT3541 since it was introduced. The Systematic series was updated for 2012, but not the Mountaineer series.
The GT3541 description at the Pro shop may be a little out of date, I believe when they say GT3541 "new" features they are comparing the GT3541 to the older (discontinued) GT3540.
If you are not going to use the center column, why not return the Mountaineer and get the the Systematic model that doesn't have a center column? An optional center column can be purchased separately later if you decide you need one.
If you are interested in the changes Gitzo made to the 2012 Systematic series click on the link below - it goes to the Gitzo website. Scroll to the bottom of the webpage for pictures of the changes that they describe at the top of the webpage.