I think your weight has a lot to do with it too. If your 5’10” and 240lb, an 8 incher will look smaller than if your 5’10” 150lbs.
I agree completely. The problem with this ideal is that most penises do not stand straight up against the body, rather, they point out, so weight seems to be the proper measure of how long a penis should be… not that I really agree with that, but it would go more in line with this thinking.
And I think an 8X6 would look big on anyone, and a 4X3 would look small on anyone.