My brothers and I we're in the scouts and my dad was a den leader. In pinewood derby season we would design the cars how we want, rasp, sand and paint them until they looked perfect to us, scouts, not parents. When that was done, my dad drill cavity in the car (one year he went through the top of a car into his hand), fill the cavity with molten lead to max weight, then we'd wood putty, sand and touch up the paint. My den had great looking cars and we dominated these races.