I have made a few without batting for summer. They work great but will offer that if you quilt with your long arm, you might have a few problems such as I had. Since there is no batting for the latching of the treads together, you might want to quilt on your regular sewing machine. Stitch in the ditch or big swirls work well. I agree flannel is too warm for a light quilt.
Best of Luck and let us see the finished quilt. Karen