Our guitarist had problems with his back, it hurt him to play the guitar for hours, so i started to look for a solution. The problem is that the weight of a guitar is distributed unevenly, so the upper body twists accordingly, which leads to tension. The solution would be even distribution of weight, and Planet Waves have devised one way to solve this problem. Some way up one strap another one is attached, that rests on the opposite shoulder.
While this means more even distribution, bear in mind, that because the second strap attaches in front of the chest, near the center of the body, the guitar is pulled away from you. It doesn't lay flat on your chest/stomach, but slides to the side of your body. It's like the metal pose, when you point the guitar - like a gun - towards the audience:) But if this position of the guitar doesn't fit your playing style, this is not something for you. Try playing your guitar pointing forward/outward, and see if it works for you!