When I was in Cub Scouts (30 years ago), the rules for Pinewood Derby were (at least as I understood them), fairly strict. You had to use the stock wheels and axles, and carve the car out of the provided block of wood, but you could weight the car any way you liked, up to the specified weight limit.<p>Given these constraints, there was one optimal design that would always win: essentially, a skateboard about 1cm thick, weighted exactly up to the limit with cast lead, with the bottom of the skateboard waxed. Everyone knew that was the optimal design, but it looked boring, and its performance was completely predictable, so almost no one used it. But every year, there was <i>one</i> kid who (or whose father) cared more about winning than about having a cool PWD car...