I think that you will also have to include Lincoln and Iredell counties to the Charlotte Metro area (heck for that matter parts of Catawba and Rowan county fit as well). When the city and the Richardson's were trying to lure the Panthers to town they went a lot farther than that in estimating Charlotte's metro population. If you add in those areas I mentioned, I will need a lot of convincing that metro Charlotte is trending Democrat.
For your consideration AG. Of course, if you expand the metro areas out enough, there won't be many rural counties left. :) Which is another thing to consider. As metro areas expand, rural counties disappear. That needs to be taken into account as well. 30 years ago, in the South, that meant erasing Dem counties from the map. (Williamson County, Tenn, comes to mind, which used to be a small Middle Tenn Dem county, that voted for Stevenson, and I think Kennedy, and now is a suburban county and heavily GOP.) No longer. Now the rural counties eaten up tend to be GOP.