I’m 5’2, medium small build, and my horse is 16.3. I know I look silly by some people’s standards, but I fell in love with this horse before I got him, and we work well together. It’s all about what you’re comfortable with. As long as you’re not 6’ and riding a 14h pony 
I love my big guy!
I am 5’2-5’3 and my previous gelding was 16.3 3/4hh I loved him. Now I own a 17.1hh DWB. I guess riding ponies for so long made me want the big guys!
I’m about 5’7" and the height doesn’t make a difference at all for me. I’ve ridden 17" horses that look WAY too small under me and I have ridden 14.2 that look just right.
My OTTB is about 15.3 (at most), but has a very deep heart girth and he takes up my leg beautifully. He is rather slab sided but I am completely comfortable on him. (I have arthritis in my hips and back, as well as fibromyalgia) The big round horses just make my hips ache. So, I don’t use height as a determining factor. That being said, my happy height is around 16.1 or 2. 
5 ft with 18h and 16h jumpers…
I’m 5ft and ride two horses: one 18h german bred mare and another 16h selle francais gelding. Even though the mare is bigger, she is easier to ride due to her good balance and easy going personality.
I must admit that I do have some post here about two years ago asking the same thing because there was a time I thought I wouldn’t be able to keep on her back over jumps, but time is proving otherwise. I recently am showing her in the 1.40 divisions with no issues.
I guess it depends on the horse’s build and balance, your comfort level and the rideabliity. My mare has an uphill balance, is light to aids and pretty quick off the ground (although not as much as some lighter horses). Large, big bones horses tend to be a bit more clumsy and take a year or two more to understand where each part of their body goes. Usually they grow for a longer period of time so it takes them more to adapt.
If you find something you really like and feel comfortable with from the start, then I’d say go for it, since many posts here have shown it is possible to do (if not, look up Margie Goldstein… 
).
There is one more perk: jumps look way smaller when you are riding them!
Good luck horse hunting!
I’m posting a vid of me riding my mare so you get an idea of how it looks. It’s one from last year because I haven’t had time to upload more recent vids:
https://www.youtube.com/watch?v=KN3_fh733Ps
Edited to add that one of the major difficulties I have found is making her fit in tight combinations (not lines, though, since good equitation can make their stride quite adaptable). Short combinations with my mare test her ability to balance quickly and shorten her scope/stride, which is an issue when horses are so big. They also test me since I have to not only keep my cool with pace (when entering a combination you must enter very controlled or you can turn a two stride into one on no time…been there done that!), but also recover my balance extremely quickly to help hers. You can see in the vid that I was unable to straighten enough in the second part of the combination and that made her get two close. Even though they are big, your balance and control is key.
