[Warren]

When making a skylight they have a template that holds down the plastic around the edge and actually presses downand seals it against the table. Then in the middle of the table is a hole the air comes up through. You have to adjust the air so it only uses enough pressure to stretch the plastic as far as you want and let up when it gets to the height you want. For the dial I wouldn't use air because it makes the plastic higher in the center than around the edge. For a dial I would use the way oldrestorer did it except heat the plastic in an oven instead of using the heat gun.