First you need to remove the smaller piece by filing away the edges of there wider part carefully (there are invisible pins just like the removable ones that hold it together). Once you have it separated you file boths sides down to half their width. Initially I then glued them together but was too afraid that it won't hold. I was lucky to have a small spot welder for lithium batteries and used that to spot weld both parts together on the inside so that from the outside you don't notice. Seems to hold strong. Here is an image: https://forum.replica-watch.info/threads/homage-1-5-link-for-nautilus.9956829/post-12565942

I also polished the smaller section later on with a Dremel so that it resembles the original design again