I wouldn't do that. I don't think people will notice, at the funeral, if you have 20 pounds less or 20 pounds more.
the SN dose is calculated way above lethal dose, which is 0,1g for every kg of bodyweight (7g for a person who is 70kg).
they recommend, for CTB purposes, 25g for people who are less than 100kg, and 35g for people who are more 100kg. failing will not happen because of one's bodyweight.
when one fails, it's usually because they either (1) vomited the SN, or (2) were found prematurely and taken to the hospital, sometimes both. but not because of their bodyweight.
I'd do the opposite: knowing that I will be dead for sure, I can eat whatever I want now. in whatever quantities I want. this freedom is priceless.
not only I'd do that, but I actually did it, I've been having this exact freedom for a couple of years now, because I gave it to myself.
I'm not 100℅ free only because, although I can eat whatever I want even in large quantities, I limit the number of meals to a maximum of 3 meals a day, with zero snacks.
but two of my meals are huge (really grotesquely big), so I still feel free even with this meal frequency restriction I created.
and I can tell you how better I feel way now compared to before when I was a dieter.
I feel so better, that I can't even find words to describe. it's just priceless