I recently finished a quilt with 8 inch circles. What I did was to cut out fusible (Steam-a-Seam 2) in the circle shape, but I also cut out the middle of the fusible before ironing it to the fabric. All I left was a 1/2" or so around the edge. It was enough to adhere it to the background, yet did not add any bulk. Then I did satin stitch around the edge, using Stitch & Tear stabilizer on the back. It comes out really nice, no puckers. If you are doing several layers, you might want to try something like that to reduce the bulk.