UPDATED:Im getting my OWN horse

[Suki Wingy]

Another thing I was taught is that if you can rest your chin on a horse's back without bending down or standing on tiptoes, it's the right height for you

then Solo is way too small, and Chopin would be slightly tall! A lot of it has to do with the horse's barrel, and how much there is to wrap your legs around.

[Tralee]

I think the size of horse is more dependent on what you are comfortable with. I know some who is 5 feet tall and rides a 17+ hand draft tb cross ("American warmblood") stallion. She is doing extremely well showing PSG.
But, I don't think really tall or big people should ride ponies and I don't think that really short people should be riding 17 hand horses. But there is always exceptions.