igedwa,
i didn't mean to imply that you were wrong; in fact, i agree with what you said. i meant to say that i believe that your use of the exaggerated example of a true triangle (or rectangle, more accurately) is inappropriate in that it's too extreme.
the big portions and small portions aren't disparaged enough to create the same problems that a triangle would, even in large rings.
though, i can't say this from experience, as i only rode a 42. but from what i penciled out, things would still be safe at larger ring sizes.