If you try it, you will see there is a little difference between what you have done, and what you are asking if you need to do, visually. If you have the center poly set to 1 and two, then the edges around those faces it are considered marked as 2^1 + 2^2 in value. That means that it matches bitwise both 2^1 and 2^2, so what you will see is a rounding around a four part poly like listed below, which forms a U shape, starting at 1 and ending at 2.
1 2
1 1+2
It isn't so much the faces you are giving a designation to, but the edges. It might help to think of it in a pathing perspective. If you have water on the surface, it can flow across any edge which is attached to a face containing a green light, even if it also has a red light. In your example above, you will have a path somewhat like this.
│││
├┼┤
│││
bah, I can't seem to change the line height...
The only difference will be that if you do the center right and center left polys as 1+2, the corner may or may not take up a sharp appearance, which can make it appear to go up or down (toward the camera) depending on the camera angle and nearby light sources.
Given that, the only thing you can really do is try both and see which you prefer. Your sphere should be able to show you some of it, but another test on a surface like a shield might show you more. Not completely flat, but only slightly curved.
I've had to play with that a lot when I was doing some of the female armor parts I was showing yesterday, which was years ago. I previously used those lines to show me more clearly in game where my texture needed to be divided. If my pixels hopped over the line in-game, I could see it very quickly.
