DebbieG -
You want to use something that has enough stiffness to stay flat while you turn your edges, but is thin enough to not add stiffness to the final quilt. I would think that a lightweight interfacing, at least the ones that I use, would not be stiff enough for this. The specialty stabilizers designed for this purpose often will wash away or mostly wash away, so you get the stiffness you need for turning the edges, but the softness that you want after finishing the quilt. So you might want to add a washing or soaking step to your tests to see what your final results will be like.
Let us know what you find out!
Nancy