Before you do what tom suggests, i've seen videos on this before. To get each side of the car symetrical you have to draw a pattern on paper. Then you get a pinwheel and trace your lines. Then you position it on the car and use chalk dust on the perforations. Remove your paper and then you can tape off. This way each side will be the same.
"Well done is better than well said." - Benjamin Franklin (1706-1790)