It makes sense, but there's currently no way to move or resize the layout elements automatically when you resize the columns. What I would do is resize the lyrics to fit the full screen without the song list, then when the song list appears it will push the right side of the lyrics off the screen, but this shouldn't be a problem assuming you only want to see the song list long enough to select the next song.
If you add the Open Song List button to the Document Only layout instead of the Perform layout, the lyrics will already be sized this way.