Sue,

It is a bit counter intuitive but aerodynamically it is best to have the big part at the front for relatively low velocity airflow. A perfect, smooth teardrop or raindrop shape (blunt front, tapering to the rear) is very low drag with a drag coefficient of about 0.04. Reversing the shape would drive the drag coefficient to probably double it (depending on the specific shape).

For comparison, Formula 1 racers (small front, large rear) have drag coefficients around 0.7 or higher. A Toyota Prius with a blunt front and tapered rear (sort of) has a drag coefficient of 0.26. The Prius depends on an aerodynamic "tricK" to create a static pressure area behind the car so it appears longer/more tapered to the air flowing by.

-Eric