I've also owned, and since regulated to the refugium, Blue Cespitularia. I ordered a small frag from Pacific East Aquaculture. Beautiful coral with some amazing color under the right lighting conditions. However, it too is a quick grower. Spreads also and can cross gaps as the base spreads.
Not trying to change your mind because they are great corals but if you look at an older image of my display you can see the green arrow. That is where I placed the Xenia frag. Look at the red arrows now. I didn't put it there. It floated about and made its way there. I saw a small flower/stalk and left it alone and it grew. It was a lot worse than this to the point it was covering test sps frags I had that I forgot about since they covered it up.
By manual removal I would have to reach into the display after gloving up, use forceps, clamp at the base of the stalk as close to the rock as possible, and gently lift left and right pulling it off. A lot of times it will peel right off with a clean break. Others you will have fragments left behind. If you leave those, they will grow back. You have to superglue or epoxy over it. Another thing I've used is f-aiptasia. That is a bit more slow going.
Now my display is iradicated of both Xenia and Cespitularia because both my Zoster and Pyramid butterflies eat it. It is safe in my refugium so it stays there

My point in the long post is I do not believe, in my experience, that you can really contain it. It will find a way to spread. And if you don't want to deal with that potential issue later it is best to not put it in. There are some other corals that may be better suited.