like mts said, you may need to shorten your stitch length. also try backstiching the beginning and end of each seam. That said, If your piece is to finish at 4 inches with a quarter inch seam you add a half inch (2 times 1/4). If you want to use half inch seams you would add 1 inch (2 times 1/2). When you increase the seam depth you add extra weight and bulk to your quilt. this will make it more difficult to hand quilt, and could cause problems even machine quilting.