I have, and the recipe was a failure, HOWEVER, I don't remember why as I did not write down why the recipe was a failure, just the note- YUCK! So the jury is out.
It's my understanding that magnesium chloride does not completely dissolve in water. That could be your problem. I would try dissolving it in oil, instead, before deciding that it's the lecithin.
Dang it, Iolite, now you've got me into experimentation mode... :)