I'm 6'4". I started high school as one of the shorter kids in school and I left as the tallest Between the ages of 15 and 17 I grew a total of 9". My body never really filled out until I was in my mid twenties. No matter how much I worked out I couldn't bulk up. Unfortunately, now that I am in my mid-thirties I am still filling out, just not in the ways I'd like.
As for the perfect height, Since my NBA career never panned out I actually wish I was an inch or 2 shorter. As it is now, it is difficult to find shirts that fit, rides on airplanes are usually uncomfortable and so on.