When I deal with this type of thing, I will find a border area with a straight or almost straight area to align the quilt then go back up to baste the rest of the scallop to the back. I use my channel lock to do the first alignment. It usually works well. I will also use the vertical channel lock to align the sides in the same way. Lately, I have been basting the entire quilt when there are issues like this, and then go back and quilt the quilt as needed.