Step 2 - Vest:
Now lets make the two front pieces.
The top width (1) should be the length from your neck to the end of your shoulders (probably about 4 inches)
The left height (2) should be the same height in the last step, from your lower back to the top of your shoulder.
The right height (3) should be however big you want the arm holes to be. I would suguest having that about 10 inches.
The bottom width (4) should be about a forth of the length across your stomach, plus about 2 inches, so the vest can overlap some.