I'm on a similar situation. I'm on zolpidem (I know actually not a benzo) and I will try partial hanging soon. Well, in my experience the only thing that bother me is SI on last seconds of consciousness, it always fucks all. I took benzos before but I'm new for zolpidem, and I find it very effective to put me into sleep, quickly. I was thinking about take zolpidem before hang myself, but there's a problem about it: zolpidem make me sleepwalk! I blackout and do things that I can't remember, is like I'm other person, so weird. So I don't know if it could help or no, as I'm not going to do it at home it can bring me problems, give up or attract unwanted attention...