It is always advisable to cut your squares about an inch larger than the final square size, that allows for any draw-up that you might have while quilting. If you are pulling your quilting stitches too tight that will cause a distortion. Also, make sure that your square is cut as near as possible to the on-grain directions. If the backgound is cut on the bias it will distort in one direction more than the other. Also, start your quilting in the center of the piece and work out all around. I do not use a hoop, but do lap quilting and I pin baste about every three or four inches and sometimes I thread baste, starting from the center and going out to the corners than filling in with basting threads between the "spokes". Good luck.