I would agree with looking for something slightly bigger, however, I would just like to add that height doesn't always mean much. I have ridden a 14hh QH that I was perfectly comfortable on (I am 5'5 and 150 lbs) and I have also ridden a 15hh horse that I thought I was going to break in 2. It depends more to me on how stocky and strong the horse is. You can go shorter if the horse or pony has big bones and a thick, sturdy body.