I read and then couldn't find the thread on an adult on a 13hh horse when I went to my photo album and came back. Here is my sister on a Quarter Pony I bought for my Granddaughters and Greatnephew. I did ride this pony. All 5'5" and 140 pounds of me many times to keep her from getting soured by not being rode consistencly.
The bottom picture is me and my Candandy. In some of my online albums I would put a couple of pictures together to be conservative of space.