Stiffer rope will be easier to flip up the tree as you advance your tethers, also if your planning on using a loop of your lower tether for your foot loop, smaller diameter ropes will be pretty uncomfortable to stand on. I use a muddy lifeline, 9mm-ish, cut into two equal length tethers and with a blake's hitch forming my foot loop, I wouldn't want to go any smaller than that, I may move up to a 10mm rope at some pointSo I don’t see many people using 8mm and 6mm ropes for 2tether. Why is that? Are larger diameter ropes easier to work with? I only ask because I considered making a set specifically for 2tether. Thanks!