I don't do show quilting (yet!) but I have certainly had to deal with the wavy borders before. You could try spray starch and a hot iron, or just lots of steam. I just did one like that last week (and I measured! still came out wavy). I used a stencil in a "C" or wave shape (from Joann's) and nothing more. I think the light quilting makes it easier to ease in the wavy parts. Best of luck with it - send pictures!