My penis has a fairly strong U-curve, and I notice that when I measure myself pressing my penis flat against a ruler, I'm almost 1/4" longer than when I don't. I often wonder if this isn't partially responsible for differences in self-administered measurements and scientific surveys (other than the fact that guys tacking on two inches to their real size so they can seem like real studs in a huge pool of anonymous data.) Is the measurement you get flattening out your u-curve the correct measurement?