Anyone have any Pinewood Derby tips/tricks?

This is a bit late but if anyone is interested check out the video of the cars my students build. I use pinewood derby to teach the basics of body work and design.
[ame="http://www.youtube.com/watch?v=0d1u05IQn4g"]http://www.youtube.com/watch?v=0d1u05IQn4g[/ame]

[ame="http://www.youtube.com/watch?v=0d1u05IQn4g"]Muscle Cars & Hot Rods Kempsville High School 3 - YouTube[/ame]