My original plan was SN (I even ordered it), but after reading that it can take up to 20-30 minutes to fall unconscious along with many other nasty symptoms I decided to switch to hanging. As long as you aren't found and the knots are properly tied it is 100% certain CTB method + as far as I know it takes 5-10 seconds, meanwhile with SN I know that I will 100% panic and call for help.