We had this article a while ago about that dwarf that ran the Boston Marathon. Lets look at the opposite end of things. Here's a 7 foot Dutch guy who's muscle balance was basically non existent.
http://spotmebro.com/dutch-giant-olivier-richters/
Being tall myself I have to admit it is more difficult to put on muscle, the same 20 inch arms looks giant on an average guy but just normal on a tall guy.
Lessons learnt:
1. Nothing beats consistency. train day in day out. Month after month, Year after year. Lifting is a Marathon, not a sprint.
2. No matter your body type, you can always improve.