I kinda know a bit about this Hugh. People grow in height by extending the bony length towards the ends of their long bones' cartilaginous areas-the "growth plate". Bone itself cannot grow in length; only the cartilage can ossify, ie turn into bone, thereby increasing height. Fact is, by age 18 the vast majority of growth plates have disappeared and are all bone. There is no more growth in height after that. Thats just the way it works in humans. You may have been an exception; there are always exceptions. Again, I am less concerned about his height as his heart, talent, and work ethic. Now, in fact, am not concerned about him at all.