There doesn't seem to be any correlation between the size (height) of a woman and the amount she can accomodate. One of my ex's was only 5'1", yet there didn't seem to be anything too big for her to handle (to the point of her having a large dildo in at the same time as I was all the way in). At the other extreme, a girl I was seeing for a few weeks, who was 5'9", always developed cystitis after we'd been fucking (I tried not going all the way in, but she was into s&m/pain and would encourage rough, very physical fucking. In situations like that, it's easy to get carried away and forget what the consequences afterwards will be). In the end, she had to go to the doctors because she was getting blood in her urine, presumably due to brusing bad enough to cause some bleeding.
Although that wasn't what caused us to break-up, it didn't help as if you care for someone you don't want things like that to happen to them - incidentally, she's the only woman who's been game for anal sex with me; even though I didn't go much deeper than the head, she ended up feeling sick for the rest of the day afterwards from the discomfort; that incident pretty much resigned me to not ask women about anal sex, but to leave it to them to bring up the subject if they were really into it (which none have - c'est la vie!)- as I said, if you care for someone the last thing you want to do is hurt them.