I'm not sure just how this was done, but I read a while back that someone did the same thing with no extra fabric. That person took another strip wide enough (with seam allowance, of course) to sew to the original binding strip to make it wide enough for double binding. She said she loved the look--it looked like she had added piping around the quilt before it was bound! I guess it would depend on the colors used. But I would suggest if the binding is print, then use a complimentary solid color for the extra fabric. Also, I suggest that the added fabric strip would be on bottom of the folded binding strip that is sewn to the front of the quilt before turning to the back so it shows up on the front of the quilt. Guess it wouldn't matter. But that lady said she loved the look so much she was going to add it to other bindings in the future!! Just add a little piece to a little piece of the binding and "audition" it first before doing the whole binding. And, do let us know what you think if you try this trick!