Originally Posted by Adraco

Given that the difference in girth between 5 and 6 inches isn't very much also taking into account the flexibility of a normal vagina I would say that very few women would be able to tell one from another, unless the penises come right after each other.

Draw it up for yourself, one circle with 5 inches girth and one with 6 and then measure from the middle out to the border. And you will see that the difference on each side is very small.

And yes, female anatomy is one of the last classes of Med. School, to avoid people "just being curious".