I'm not an experienced quilter, but the suggestion to quilt a flannel sheet at 3 to 4 inches seems excessive. It's not batting, so it shouldn't shift. As long as the sheet is washed and dried a couple of times, it should not shrink any more. I generally use Warm and Natural batting and it says to quilt it 25 cm apart, which is a little more than 9 inches. Why would a flannel sheet take denser quilting than batting?
bkay