Hope you're only 4 feet tall then... (Score 2, Insightful)

12 feet is the "circular equivalent diameter" of their biggest pipe... which I read as the diameter of the circumscribed circle around this elliptical shape. Cut that circle in half, and we've only got six feet.

Since we're dealing with an ellipse, cutting it along its major axis will give us even less than that for headroom.

Hobbits only, please.