i may have missed this while i was gone but has anyone suggested finishing the waves by using a facing instead of binding? this would keep the off-grain curved edges from, hmm, waving.
simply cut another layer of fabric, backing or coordinating, using the existing edges as a template. sew, right sides together, 1/4" from raw edge, clip where absolutely necessary, turn, topstitch or handstitch 1/4" in from the edge to hold in place and hem on the back. makes a nice frame if you use a different fabric than the quilt back. this is a commonly used method for finishing an odd-shaped edge.