Thanks for the video!
I wish I had seen this before I ended up trying to use my own workaround. I ended up applying the mirror modifier so it became part of the geometry. I then duplicated one of the strips for the back middle. As a result, I couldn't use any of the mirroring features for the rest of the tutorial but I wanted to resolve this. I also learned a lot through this process of trying to figure out what I could do to fix it.