Yes! It must be clamped down and then aligned with the mirrors. On my machine, there were 2 layers of padding between the mount and tube. I was able to remove one layer and still be able to safely clamp the new, larger tube in place. If that is not possible in your case, you can find patterns and files for new mounts on the various laser group pages.
Be extremely(!) careful - you can easily crack your tube if you force it into a 50mm bracket. you must pad it or use a dedicated 55mm one instead, and it goes without saying that you will need to tilt / lower it to not only hit mirror #1 dead center but also to be parallel to all the rest as possible.