thanks for the tip, i learned something, too. i like the idea of the paint sticks. i have had the clamps stretch the fabric out of shape and couldn't figure out what i needed to do different to stop that but still keep it smooth.
a pro quilter told me to mark centers on top and bottom edges of the quilt top. fold in half and match the centers. then check the side edges to see if they are even. but she said the best way to get a square top is to make sure all the piece work is squared to the same size before it is put together.