A few years ago, I bought a Gitzo 3530 carbon fiber tripod. It was one of the first Gitzo 6X series models. I chose it because the dimensions very closely matched my older Bogen 3221, which suited me well. I got a model with a centerpost because I find a small amount of vertical adjustment useful when doing closeups.
However, the Gitzo centerpost was way too long, and just one section. It would not let me get low (I could not even spread the legs to the second position with the post all the way down). I didn't want to spend another $100 (USD) on a shorter post, so I cut mine to match what I used on the Bogen.
I had never owned anything with carbon fiber prior to this, and I was surprised at how easily it cut with a hacksaw. I filed it carefully. I still wanted to use the hook supplied with the tripod, so I also had to file away the carbon fiber where the post attached to the connector (where the hook screws into the bottom of the post). That took a little time, as the epoxy holding it was quite strong. Then I used fresh epoxy to put that piece back into the bottom of the shortened centerpost, and let it cure for a day. I find it much more usable now. I can still remove the post and go to ground level if needed, and the little extension left is just right for me.
Here's the result: