Bro, I am pretty sure just about everyone on this forum will tell you they have the same problem as you. IMO no one is completely symmetrical. I see this in the gym all the time where guys will use heavier weights on one arm because it's lagging behind the other. I laugh, because it's in our genetics and it's just the way our body is. I don't think you will ever get the same shape with both arms. I would really like to see what others have to say regarding this issue, because I really don't think it's something that's totally correctable.