Gitzo GT1531 sturdy enough for Canon 300mm f2.8II (when it's out)

I'm looking to get a new tripod for my wife. I would like to get about the lightest tripod possible that will still have enough stability. She currently uses the 100-400 lens on a 7D. In the future I'm considering the Canon 300mm f2.8 II lens for her that will only weight 5 pounds.

In your opinion do you think the GT1531 Mountaineer 6X Carbon Fiber Tripod is suitable for that lens?

Thanks
Doug

Thanks for the response Peter. I had some responses from another forum and they were convincing for me to lean toward the 2531 for extra stability. The 3541 would be nice but the weight is more important to me.

Thanks again.
Doug