Uppy- check out this thread I started when I was looking into a set as well. I think the PSer you are thinking about is BurberryGirl who has several stacking carbon/ sugarloaf rings.
Hope this helps!
Sarahbear, those are beautiful!! I've taken a look at my silky neon mahenge in a foil bezel, and I'm not liking how it loses some of its life. I think I'm going to have to have some sort of prong head for her. I've also got a neon chrysoberyl that I was thinking of stacking with her. But I also think I need a very saturated (not dark though) amethyst to round out the color scheme.
I wonder if there are any other etsy designers who do stackers that are either open bezels or prong?