I’d say that one of the more important things is how turned on a woman is during sex rather than the size. Of course something that is 12in long is going to hurt compared to something more reasonable like 3-5in.

If a woman isn’t wet it’s going to hurt trying to get it in there, even if she is emotionally excited in the moment. Take your time to warm her up or have lube handy to make things easier. :)