Self portrait of Leonardo da Vinci?

The Turin portrait drawing is generally accepted as the self portrait of Leonardo, but I must agree with the author, Robert Payne ("Leonardo," © 1978 Doubleday & Co. Inc. garden city, NY) that it may be of Leonardo's father's portrait. Leonardo's father had lived to be 80 years old and died on July 9th, 1504. The drawing is thought to be made about 1512. I feel that this was made between 1511 and March of 1513. There is a possibility of Leonardo reminiscing about his deceased father while Leonardo was in Firenze, pursuing the lawsuits against his brothers about the inheritance.  There are some odd elements in his portrait (if this was the self portrait). I know that he was known to appear older than his actual age, but around 1511-1512, Leonardo was about 60 years old, so even after considering the above fact, the man in this drawing appears to be at least 15 to 20 years older than Leonardo. Although it is a quasi-myth/legend, we know that the face of Plato in the "School of Athens" painted by Raphael was based on the portrait of Leonardo. It does somewhat resemble the portrait sketch by Leonardo, but one thing is quit different, and that is the shape of the nose and the nostril.
All the other artworks, whether it is the young figure in the "Adoration" of Leonardo or Verrocchio's "David," the shape of the nose is similar to the one painted by Raphael as Plato. This is also pointed out by Payne as 'curving nose' of he portrait and the straight one in the other drawing(s).