The community thought I was crazy, said it was impossible, but I achieved it: I have intentionally triggered sleep paralysis.
I won't say it took a lot of practice, though I will say it took some doing. I don't really know how to explain it (which makes this whole writing about it deal difficult), but if you have any experience with metacognition, you may be more able to achieve the desired effect.
It wasn't so much thinking about how I think, but thinking about how I feel (in a tactile sense). Sleep paralysis isn't true paralysis, only the sensation of it, so I created a scenario in my mind where I couldn't move, and tried to replicated it externally. It's not dissimilar to my astral projection proposition.
Lo and behold, it worked. Not right away, but it did work. And after some experience, I can replicate it without needing to go through the whole mental rigamarole, even selectively, which is a real handy trick if I expect to be sitting somewhere for long periods. I just numb the area that's not going to be doing any moving (takes about ten to fifteen minutes for the sensation to kick in) and then I don't have to worry about muscle or joint discomfort, pins-and-needles, or any of that jazz.
Not that I felt much concern about the effect, I feel none at all, which was the whole point: one of the best ways to eradicate fears of something is to learn how to control it.
If you want to try it out, I wish you the best of luck. If you have any questions, I'll answer them to the best of my ability, but I can't make any promises.