I have always pressed my bindings in half; if I sew it on the back and machine sew on the front, or if I sew it on the front and stitch-in-the-ditch (SITD) from the front or hand stitch on the back. My bindings never "bunch up", so I don't understand that. Binding fabric is so thin that I don't see how there can be a problem. I have had the problem a few times that the binding didn't stay flat...the top layer seemed to have more fabric than the bottom. I solved this by giving a little stretch to the binding as I sew it on. That way you also don't get wavy edges either. The binding is nice and snug.