Carol, what about using some of that pre-made 1/4" wide bias strips designed for use on stained-glass style quilt tops, or making bias strips yourself, using one of those 1/4" bias strip makers to make it even. These are available online at Nancy's Notions, I think. If you get the widest double needle to sew it down with, you can do one, even pass that sews down both sides of the bias strip. And if you baste it down with either glue basting or fusible web, it would stay put while you are sewing it and it could only add to your lovely geometric pattern. Just an idea.