I find the best way to get my tops and bottoms to not pucker or sag is to stretch them on a frame. I have had pieced quilts tha will absolutely not lie flat without being stretched. I have the Flynn system for small stuff, which works well, but I have to pin the large stuff when using the system because of the size under the machine. I have a quilt frame for the Pfaff Grand quilter, but it doesn't work consistently for me. Does anyone else have that problem with the smaller quilting set ups like the long arm without all the bells and whistles? I guess I just have to practice, practice, practice.