I don't own a HiPo but I have a friend who does, a little grey dun called Gracie. Miss Gracie-fluff is about as wide as she is tall. It's my new fav pony breed! She is such a boof-head too, she's 13.2-ish and in a full sized halter! But it's a lovely head and in proportion because the rest of her is so large.
Haha. That's so lovely to hear! My boy is HUGE! He's over height as they aren't supposed to exceed 14.2hh but he's 15.3hh! He's got a huge head too and is very difficult to get tack for. He also takes an 18" saddle. He's a great big lumbering boy but SO comfortable to ride and I wouldn't swap him for the world. My friend has a mare who's only 13.2hh and she looks like a foal in comparison. Haha.