The relevant threads had varied opinions— some said mild panic and shortness of breath. Some said pain and nausea and took quite a while. Some said it was painless and fast.
I cant find the latest copy of the PPeH either.
Search the forum and you will find links to the latest PP(e)H. There is also a cleaner copy
here of just the Lethal Organic Salts (Cyanide/SA/SN) chapter by a forum user who has done OCR and assembled it as a website.
Something like SN suicide, which occurs in secret and often unwitnessed, where the successful victim can't report back and even when used by proper euthanasia organisations is done fairly infrequently by global standards, is not going to have the same absolute scientific consensus of information that other mainstream medical topics do. So there is always going be a small degree of uncertainty present. The physiological mechanism of action is well known and well-explained.
The subjective effects felt by the victim fall within a narrow but admittedly not insignificant range of symptom severity that is covered across the PPH, the SN guides here and the written experiences of people who used the method or witnessed others doing so. That range of experiences may well be due to different physiological and emotional states of the victim, rather than any one account or description being incorrect or inaccurate.
When deciding whether to use the SN method, you are best to take all of these possible scenarios into account and making sure you are comfortable with the possibility of the least pleasant one as well as the most pleasant.