Tom, perhaps you missed the part where perspective doesn't explain why the sun hits the horizon in the first place. Perspective will never allow an object above the horizon to appear to sink below the horizon, regardless of its size.
In Earth Not a Globe we learn that the Vanishing Point in perspective is a finite distance away from the observer, and not an infinite distance away as taught in art school.
Please read Earth Not a Globe and grasp the material rather than asking the same dull questions year after year.
I've read the appropriate sections of ENaG. Rowbotham is wrong in his interpretation of the vanishing point as well. How can the sun appear to set below the horizon due to the vanishing point when the atmosphere makes the sun appear bigger? Seems like a contradiction to me.
When I watch the sun set below the horizon, I'm not watching the bottom part of the sun fade away as the sun recedes into the distance, I'm watching the sun move downwards. Frankly, bendy light explains this phenomenon better than perspective does.
Oh, BTW, perspective doesn't explain why the sun rises almost exactly due east and almost exactly 12 hours later, set almost exactly due west to observers all over the world on the days of the equinox. Perhaps you can refer me to Rowbotham's explanation for that one too while you're at it.