I am 5'2' and have always seemed to have trouble taking cocks longer than 6 inches.
Girth wise I don't have problems at all- once I am aroused and wet enough I could take any girth.
I've found that, when I haven't had sex in a while, I tend to tighten up a little, but after a good foreplay (maybe with some toys involved) I am good to go again
A very good friend of mine is about the same height as me but much thinner than me (I am usually around 120 and 130 lbs, but very curvy) and she is totally into really hung black guys. She has 3 kids too, so I am not sure if that is an issue or not, since I don't have any yet.
But I remember a few years ago, we both had a little no strings fun going with this hot Latin guy we both were friends with. We didn't know we both slept with him at the same time, but when we found out I told her I loved his dick and that he almost hurt me the first time we had sex cause he was so thick. And she said: Ah, I dunno, I think he's pretty small......at least compared to the guys I usually have sex with!!