Hmm. I guess I would quilt the center as a stand alone piece. I hope that you made it larger than needed. Then I would temporarily bind the edges & wash it twice, like you did the original. Then I would cut the center to just fit the opening, and use a large zigzag to secure it to the border. You could also whip stitch by hand. Then apply a trim strip over the seam. Make sure you have laundered the fabric for this strip also. Cut it twice the width you want, then fold both sides in to meet in the middle. You can top stitch this on the front, and will probably need to hand stitch this to the back. Good luck. The new church center is really nice.