Are you asking about using 2 tethers and 2 sitdrags in case the main tether fails? - I have thought about a second tether but have not done this and do not plan to. Too many ropes. Some just leave the lineman attached for this situation. (I do not as I do not want it to show movement and noise on the deer side of the tree.)
Or 2 sitdrags on 1 tether in case the main sitdrag fails. - for this I use a rock climbing harness that attaches to the main tether line but a little lower. It has less than 1" slack. Should the sitdrag fail, I would fall 1" before the rock climbing harness catches me!
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