I am hemming a length of fabric for the sides of a simple drapery panel. I carefully removed the salvage edges first by cutting away 1 in and then hemmed these side edges. I pressed the hems when I was finished but the hemmed sides still "pull up" shorter than the rest of the width of fabric. Can anyone give me an idea what is causing these hems to do this? I so want these drapery panels to look nice. Thanks in advance for your help.