I'm making two roman shades that are approx. 65" in width. I had to piece the fabric to achieve this. Now I have to cut down the width to the required 70" width x approx 65" length. I always have difficulty with cutting large fabric panels so that they end up squared correctly. Due to the size of the fabric I'm working with, would it be precise enough to fold the fabric across the width and measure/cut it that way? If so, would I pin the selvage edges first to keep things together? Any help in this area would be greatly appreciated, as this is always a challenge for me....

THanks so much ahead for any help you can provide.