You can use the Loupe Overlay feature. With the image in Loupe view in the Library module, or in the Develop module, choose the command View > Loupe Overlay > Choose Layout Image, and load the magazine cover layout overlay.
I just tried this out, and noticed something important: The Loupe Overlay does not work in the Live View window for tethered shooting, but if you just take a tethered shot, when the shot shows up in Loupe view or Develop you will see your Loupe Overlay image over it, and use that to adjust the in-camera composition for the next shot.
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