Is this horse too big?

Oh, get a step stool, get on him and go ride. If you like him, get him. You can't see yourself while you're riding him and most people are only going to notice that he's a well behaved quality horse. The ones that worry about you "fitting" your horse are also the ones that are going to care that your boots aren't the right make and your bridle is the wrong style, and that your stirrups are more than three months old, and that you wore that blouse last month. Do you really want to live your life for those people?