yeah, i wouldnt really trust that. I cant see the average woman finding a 9x7+ perfect. That won't fit in an average woman, lol. Nothing wrong with having that size at all, I just think the average 'size queen' finds that ideal.
To each his own though(or her own). Some women might think a 13x8 is perfect while others think a 7x5 is just right. You can't really average out those numbers to say what is ideal and what isnt. It needs to be taken on a case by case basis.