I have the HSS vest. Attachment point is top center of the back. At the bottom are crotch/harness straps. So, if I were to fall, I'd be hanging from the tree, completely vertical with the weight being supported through the crotch. However, once in the stand and attached, if set-up properly, you aren't gonna fall any lower than the platform you are standing on.
remfak touched on an important point. When you set your safety harness, make the height so that you can't fall completely out of your stand. You should be suspended close enough that you can raise your foot and step back on to it and relieve the pressure to avoid the problems mentioned above.
