When a final print is viewed from a substantial distance, that elongation (away from center) is obvious. But as the viewing distance gets closer, the outer edges of the print are seen at steeper angles, and the original elongation becomes visually compressed. At the exactly correct viewing distance, the heads will visually become correct.
I now understand more clearly why Mark kept saying "Just try it."
Not so - the distortions are in opposite directions, they will cancel each other out.If the print is already distorted because it was taken with a wide angle lens, they will even look more distorted.