Typically I use smaller amounts of fabric so maybe this helps, but I think you are having a problem with the fabric being off grain. Don't assume the fold from the bolt is accurate. To those of you who were horrified when your fabric was ripped at the fabric store, it will ensure a straight grain. The salvages are not what to use. You should use the torn width of the fabric, remove the selvages then fold in half and press the center, it probably will not be the same as how it was folded on the bolt. Hope this helps.