I just finished up the top of my third bargello and when I hung it on the desiign wall, I noticed that it's a little bowed. I was overly cautious with the individual strips and I've never had this on the other two bargellos I've made but this one is bowed. I've tried stretching it and it stretches to the right position. I think it's because it's a smaller bargello (sort of like a postage stamp quilt). How can I fix it? I've thought of steam ironing it but not sure.