actually, its straight up the leg where it enters the body...the bone angles forward as it reaches the bottom of the brisket, headed essentially in line with the top line of the neck, goes about half way to the neck, then angles back up to form the platelike bone of the shoulder blade..so the sweet spot is straight up the leg, and dividing the body into thirds with two lines - its between the two lines...that's the sweet spot.
I will try to find the skeleto-muscular diagram I have somewhere that illustrates this for us and will forward to you.