I'm 5'9" and 145lbs and my mare is 14.1. But she is very wide so she takes up a lot of leg and I feel very secure on her, even bareback. I mean, my legs do dangle down a little lower than her belly/chest area but only by a few inches and I've never been told that I look too big for her, so I'm not really worried.
I definitely second what everyone says about the horse's build being more important than height.
Also, just for kicks, over the summer, at my camp, there was a gelding that was like magic. You'd look at him and he'd be maybe 14hh, just eyeballing. But then, you'd get on him and suddenly, he was like 17hh. I don't know what it was about that horse, but when you were in the saddle you felt like you were riding a freaking giant but out of the saddle, he was short!
Another random story: at my camp there's this little QH pony who's maybe 13.2hh on a tall day. However, she is the WIDEST thing I have EVER seen (she's built like a tank, short legs on an average sized body). She's so wide that I put a long legged guy who's over 6ft tall on her over the summer, and his feet were barely lower than her barrel. It was like how I am on Lacey, only the horse made Lacey look like a giant!
Fabio - 13 year old Arabian/Lipizzan gelding
Rest peacefully, Lacey.