My mare is 16.3hh, so only one inch shorter than you are considering. People have often said things to me like "its a long way up if you come off"! Really that simply isn't an issue. I've come off her and I've come of a 15.3hh - both hurt. If anything there is more time to curl up before landing off a big one. My mare is a lovely girl and I felt safe on her as soon as I tried her. You will know when you try these horses if they are too big for you. You will either feel happy on them or you won't - go with your instincts when you try them17hh is a long drop if you fall off!![]()