I made a bunch of project bags with a vinyl window this summer and I used the tissue method to prevent the vinyl from sticking to the throat plate or the presser foot. I used a regular needle but lengthened my stitch. If your sewing line stitches are too close together you'll weaken the strength of your seam. It was a pain switching back to regular stitch length every time I changed from sewing the vinyl to sewing just fabric but that's what worked for me. The project bags turned out great.