I haven't tried it with 2 biners but I don't see why it would not work. All the rings do is provide friction to hold the straps.
I would watch the shape of the biners. Part of the reason why the rings work so well is their shape. There are no odd corners to reduce the holding friction. Most biners have non-symetrical bends to them that may tend to let you on the ground now and then. Just a caution.