Thanks again, everyone! Ellen, what beautiful quilting.
I looked again at the quilt top and it was machine pieced. The top measures 76 x 76, which is too big for me to machine quilt it unless I decide to make it a summer quilt (which is beginning to sound good!).
What if I put flannel instead of batting in the middle. And then, what if I quilt along the hexagon shapes the HSTs make and do a design in the square? Would that be enough to secure it without over stressing it?