Can ladies chirp in with an opinion?
One of the reasons i never bother taking bone-pressed lengths seriously is because when someone jabs the ruler deep into their body fat, you can no longer see the first markings on the small end, ad it would be very easy for any guy obsessed with proving his 8 or 9 inches are real to simply clip off the end of the ruler and no one would ever be able to tell.
The other reason is that though men may feel like they can compress their fat pads when thrusting, the fact is that they will never compress as far by pressing against another soft human body as it seems when jabbing a small, solid object deep into one's body fat.
Bigger guys complain that they "lose" inches, but as someone who has been both small and large, and who has slept with slim and hefty men, the fact is that an increase in body fat does limit penetration to an extent.
On a totally different note, I'm not the most visual person, but that is an aspect that i know lots of people respond to, and no matter how many inches are "hidden" under fat, if there are only 5 inches showing, there simply isn't going to be the visual thrill of being presented with an enormous, commanding cock.