I like your quilt. Love the colors and simplicity. Why not do straight line quilting just to be safe? You could follow the blocks and just sew on those lines. You would have to sew over some blocks to keep the straight lines going but that's ok. When it is finished, it will be beautiful. If that is too simple, then do something different for the border. Mark your quilt to do this and follow the markings. You can also use painters tape for guides on your straight lines. Good luck and I hope to see it finished.