I tried extending the width and length of a quilt without good results. The quilt was birthed, so there wasn't a binding to remove and easily extend the quilt, I just sewed it on the outside of the quilt. I ended up taking off the extension and using them to make a new quilt. If I had to do it again, I would rip out the envelope (edge) seam(s) and add more blocks or borders, zigzag or loosely whipstitch additional batting to the existing batting, and add borders on the back, too. I'm sure it can be done. I just didn't do it right.