He grew from about 5'1" (I'd be guessing on his weight, but he was average in build, never fat, but never slight, either) to over 5'10", 160, within a relatively short period of time and has never been either lanky or stocky, but is now just well-muscled - but no longer built like a little boy. A pretty nice athletic build, with not really an ounce of fat on him. Hard to say why he feels slow (because now he hits the ball harder and further, so it has not seemed to hurt him in games 
It's not all bad). His feet and hands still look very large to me (I suspect that he is not done growing). He does not look particularly awkward to me (oversized hands and feet aside), but he's always been very confident about his speed and it definitely bothers him that he does not feel like he is as fast as he once was. Yes, he's in a running program (his idea) and if nothing else, I hope that will help him continue to adjust to his new size.
