Courteous lies about your fat seatmate

Regardless of what the optimal policy is for dealing with tall* and/or fat people on planes, I would think that fat people, who are by their accounts embarrassed by policies that question their ability to fit into a seat, would understand that the mere word of your seatmates is not determinative of whether you are encroaching on others' space, as with Kevin Smith's recent Southwest flight:

"The people around you said they had to lean over to make room for you," Linda offered.
"Linda, they didn't! The older lady was leaning against the window like she was gonna nap, and the lady to my left was already leaning toward the aisle." …
"The report we received said the ladies were leaning away from you."
"They were already leaning when I sat down! They didn't lean because of me! I even asked them both if I was a problem."

Surely it's embarrassing, and by some lights rude, to be honest in these situations. If you're a smaller woman sitting by a very large man, would you really be likely to say "Yes, you're making me very uncomfortable" or "This is a problem, one of us needs to be reseated"? No, you'd probably be self-effacing, deny that he's bothering you, and lean away. But leaning toward the aisle is not a workable solution, unless you enjoy being walloped by drink carts and passersby. And in the brave new world of no free pillows, leaning against the window is also non-optimal (and sometimes cold!).

I've seen some people point out that men are more likely to be "customers of size" but have not seen anyone make the obvious corollary that women are more likely to be subjected to unwanted physical touching by said customers.

* Tall people who want maximum and unchanging legroom should sit in the rows behind the exit row, which often cannot be reclined. The convexity of the contoured headrest hits short little me right in the back of the head, so I recline and slouch to not have to sit with my neck permanently at an angle. Also, because I paid for a seat that reclines and has armrests to separate me from other people.