Pinewood Derby project

In the next few weeks my son and I will be building Pinewood Derby cars. One for each of us. He's in the Royal Rangers(Assembly of God version of the boy scouts) . They even have a race just for the Dad's. I remember doing it when I was in Cub Scouts. It actually brings up some mixed memories because it was a period when my Dad wasn't around(which is pretty much the norm anyway) and so the Den leader had to help build mine. I guess it's time have some father/son time. Hardest part so far is picking a design. Here are some websites I've found on it so far:

http://www.pinewoodpro.com/pinewood-derby-howto-design.htm

http://users.aol.com/randywoo/pine/design.htm#design

http://www.gospelpublishing.com/store/startcat.cfm?cat=sRRPNWDDRB&mastercat=&path=sRRPNWDDRB

http://www.gospelpublishing.com/store/startcat.cfm?cat=sRRPNWDDRB&mastercat=&path=sRRPNWDDRB

http://www.abc-pinewood-derby.com/pinewood-derby-reviews.htm

http://www.maximum-velocity.com/

I'll try and post some pictures as we go along. It should be fun.