Design Tips
1. Have your son draw a design on paper then cut it out and use it as a template. Using graph paper could make this easier.  Draw a side and top view on the paper by tracing around the block of wood.  

2. Keeping the car at the full seven inches in length makes the most of the laws of physics.   A longer wheel base makes a faster car--and helps it roll down the track with greater stability.  

3. Use the full 2 3/4 inches (outside wheel to outside wheel) that the rules give you. This will allow the wheels to travel farther before hitting the center strip.  

4. Leave a lot of wood in the back to have room to put in the weights.  

5. Use the groove closest to the end of the block of wood as the rear axle. 
Note: The Race Starter will place the car on the track according to axle location.  The back axle is nearest to the end of the car.  The front axle is furthest away from the end of the car.  This determines the direction the car will race unless the contestant clearly labels the front of the car.
6. Do not make the front of the car pointed. This makes it harder to set up against the starting dowels.  

7. Use your imagination. Be creative. Shape has the least to do with winning. A beaver driving a log or even a pickup truck is more interesting than a wedge and will be just as fast!