Before you start anything, turn the top over and measure between the parallel seams and draw a line down the exact middle of the top. Do the same on the roof of the car by measuring the center from the drip edges. This will center the top side to the side on the car. Use a regular pencil, not any type of grease pencil. Larry has seen colored grease pencil lines bleed through and discolor the top. White vinyl is especially sensitive to this.