SuzzyQ: I also took a OBW class back in March. We made the hexagons but the instructor (a LQS owner) also explained about the octoagons and told us about and even gave us a pattern on how to add the corners to them. Some of us asked about just appliquing the finished octagons onto a square of fabric and then join the squares together. She thought that would work just fine and so do I. You might be able to salvage your fabric and add some "light" to it by that method as well.
Just thought I would share.
Murphy