I think it's this "getting stretched" and "getting filled" thing that has a deep emotional effect on a woman. You can make a woman cum with less than 4 in, but this is a different story. I think with a cock that fills her out 100 % she cannot but concentrate on the intercourse and forget everything else, including hubby sitting in the corner.The average vagina is 3-4 inches long, but . The vagina can expand by 200 percent when sexually aroused, kind of like a balloon. Remember, the vagina was made to birth babies, so it's exceedingly elastic. So you guys that are hung... Fear not.
As to the cervix, fear not, the penis cannot pentrate the opening.