Hey, just got home and decided to test your idea of separate rings. I started with a normal garda hitch through two separate rings then pulled them apart and as their relative angle changed the knot deformed a little but if you use your imagination you can still see it there...
It works great, the cord pointed directly at you would be the support and the end off at an odd angle is the excess you'd pull to tighten it. When tightening the rings do a funny little butterfly thing.
From the way the rings pinch down on the excess cord you can see it would work with any angle but I would suggest constructing the hitch as you see in the pic as it is much easier than trying to keep everything held together and tighten at the same time.
I was trying to attach the pic but I've had too many beers with dinner and it's not making sense right now
, please just check my gallery and it should be the only pic"garda hitch with separate rings"