Weight in the back, good! Exactly as the poster said. Think of it this way. At the start of the race everything is equal. When the car hits the level portion coming from the incline, the weight in the back will fall even farther, using more of the stored potential energy. I designed all the cars this way. The one that won was usually even coming down the hill and it then took off as soon as it hit the straight. 3 axles also good. You are using less energy rolling 3 instead of 4 wheels. New axles locations good. I drilled the car with new axles on a drill press at the same distance as the originals.
The way the track is devised also has a lot to do with it. His den ran a 6 lane run off and a time was taken for 6 runs in each different lane. They then took the top times and had a seeded elimination. Very well run and organized. When He went to the district finals, it was a double elimination on a 2 lane, poorly made track. You could have the 2nd fastest car and not even place if you come against the fastest one in your first heat. Notice how the first track is primarily flat. Cars with weight in the back seem to do much better here. On the steeper, shorter course, it made less of a difference.
