Do you have any suggestions for fitting princess seams. I basted mine instead of pinning and had no trouble at all sewing the basting stitches. But, when I went back to adjust the seam after fitting it the fabric kept bunching and I couldnt get it to lie flat enough to sew it. I did clip the seam allowances but now that I basted they don't seem to help. Could the basting stitches be preventing the fabric from spreading out. I'm realizing that perhaps I should just use pins. Also, is it better to sew the seams with the center panel or the side panel up or does it make a difference?

Any help you can provide is so appreciated. I really want to sew a nice sheath dress.