I'm 5'5" and my shoulders are around 22". No one's ever commented, although I'd always personally suspected they were a bit broader than proportional (mostly from the way clothes fit). For someone taller, 17" seems likely to look fairly narrow, actually - plus it's about the balance of shoulders to hips as well. If your shoulders are no wider than the widest point on your hips/thighs, or even smaller, the optical illusion will make them look smaller yet.