How tall will a 5"3inch (me) person be compared to a 14.2hh cob horse?

5'3'' means you're 63 inches high, meaning that you stand 15.3 hh. so you are 1.1 hands, or 5 inches, taller than a 14.2hh cob. you will be able to see over his back but his withers will be above your chin. this horse sounds like the perfect height for you actually.