I just made these tutorials to show the method I use setup the stretchy system when I rig. The next step I am still trying to account for is matching the FK and IK stretch to be the same without having to use any scripting, as well as add elbow locking, ribbon pull offs and the IK/FK snap. I have seen some new methods that have the arm always in FK but it is IK at the same time....boggles my mind and I think the person made their own plug in for it. I will post more about that later. If anyone knows more about this do tell, or if you know a better way to setup the stretch let me know!