So, I couldn't induce syncope just by crouching, hyperventilating and then standing. It turns out you have to strain afterwards, and a reliable way of doing this is with something called a Valsalva maneuver, which is where you try to exhale against a closed airway. I've been able to reliably induce partial syncope through this process. I did it on my bed to avoid mere injury, and the ceiling above my bed is slanted, so I couldn't stand up all the way, unfortunately, and I think that might be contributing to how I was only getting partial syncope, but either way, it usually only takes two tries, at which point, I will inevitably fall over (I can guide my falling a bit, though I did still end up hitting my head on the wall very slightly), and begin to grey out. When this happens, I begin convulsing. It doesn't feel involuntary, it feels like I'm just doing it on purpose, but what I've read and seen indicates that I don't have motor control at that time. I never fully lose vision, but the borders of it fade, and I can only see within the center of it. I can still think throughout this, but it's very subdued. It was reduced to the sort of background recollection of music that I have going on all the time. I remember looking at my computer monitor and seeing the image that was pulled up, and being able to identify that it was a person lying on the floor (I was watching a video about syncope), but I couldn't remember the context behind why I had this image up, and I couldn't see well enough to tell that the person was wearing flesh-tone garments instead of being nude. I thought that it would be very embarrassing and morbid if I died with a picture of a naked dead body on my screen and people saw this. Anyway, this should be enough to prevent SI during a partial hang, I think.