Kudos to Craft Passion for making an awesome cloth facemask pattern. After working with the pattern, I have made small adjustments, which I think improve the fit and seal. First, it is hard to get the elastic length right, because head sizes are different, and elastic stretches out over time. A solution is to only tack down one end of each elastic and add a small elastic loop to the area where you would normally tack down the other end. This way, the wearer can fit it perfectly to their face by knotting the elastic to the loop, and also tighten it down later when it starts to stretch out after washes.
Second, the fit at the nose bridge of the original pattern is a bit loose. A solution is to add a plastic-coated twist tie or 16-gauge coated magnet wire so it sits between the two layers of fabrics. The kind of coated twist ties from bread bags will work. Bend the ends of the wire inward so they do not have sharp ends. Stitch the wire into a separate piece of fabric and then stitch that piece so that it ends up in between the two layers centered at the arch.
Thanks for reading.