|When sewing with silk chiffon, or any extremely lightweight fabric, one of the big problems seems to be aligning the fabric for cutting.
1. Definitely use a rotary cutter and weights, as the fabric won't shift once you begin, as it will with scissors.
2. Once you get the fabric laid on the cutting mat and generally in position, you can adjust it in very small increments by getting down to the edge of the table, and blowing on the fabric. The very light fabric will shift when you do this, and yet it will shift smoothly across the width.
These two techniques make it very possible to cut in a double layer if you like.