Aren't 1/2 inch roughly 12mm? 10 mm is pretty close. I found one model which accommodate a 1/2 inch cord but only one, unless you combine the two toggles or tie the elastic into a hanging knot one is not enough.
Another solution is using a flat elastic instead, like a 1 inch elastic band. Then there are countless of options to secure and adjust the strap! Including the use of a side release buckle, making aborting a breeze for the suicidal with doubts.
I found some fashionable elastic band with flames, but that's optional.
View attachment 136924
View attachment 136925
When the body is experiencing cerebral hypoxia and loses unconsciousness, it does so because the oxygen level is too low to support it. This is not the same as being asleep as you aren't responsive to stimuli.
So the question is really do you regain some form of cognitive functions while being unconscious, maybe manifesting as dreams? We all heard of the classic story of walking into the light when dying, maybe this is visual representation of not enough oxygen to even support the most basic of cognitive function.
I would look up cardiac arrest survival stories, preferably those who been "dead" for 5-10 min. These cases are similar enough as it also deprive the brain of vital oxygen, all through much more abruptly.
In my humble opinion I believe the sensation after unconsciousness if any would be spiritual and not painful. Dreams can experience faster than real life. I believe in this short window before and after unconsciousness these powerful images manifests, the classic light in the tunnel and seeing the loved ones for example. After entering the tunnel I don't believe there is more.
Death occurs 10-15 min later.