Maybe I would soak it in a mixture of water and some StaFlo starch. Block it and lay it flat to dry and then steam iron it. That could work and then I would decide whether or not to make it larger. I made a “Circa 1880” quilt by Pam Buda and was fortunate enough to meet her. She told our group how she starched her fabrics and ironed them after they were dry before she sewed them together. It was time consuming but it worked keeping those little pieces straight and unstretched. I love your quilt. Please let us know what you decide. I so hope you find a solution.