Saw this video about making life lines. He's using double braided poly premium rope. Is that enough for a life line? Here's the link with the video.
http://www.wideopenspaces.com/how-to-make-your-own-diy-deer-stand-safety-line/
http://www.wideopenspaces.com/how-to-make-your-own-diy-deer-stand-safety-line/