Joe, here is my advice. Pull your shoulders back, and it will take some stretching to get use to it. Get in your set up position and I will be willing to bet that your shoulders actually make a bowl shape. Think of it this way, you want everything pointing down the target line, and with your shoulders being such a vital component it only makes sense. I'm not saying to pinch your shoulder blades back until you feel pain, but pull them back until your back straightens out and your shoulders are in line with your hips...
PS- I'm not a teacher but I have experienced the same thing, I was so concerned about getting my arms close, that the closer they got the more I was rolling my shoulders forward.
Hope it helps you...