Watch the movie "Down and Derby" (google it). Parents get way out of control, building test tracks in their bedrooms, etc, very funny!
The first time we did a pinewood we won it all. With just a P.O.S. car that a Pack parent helped us add weight to on race day. We did not know a thing except to smooth the axles.
The next time, with my middle son, we did all the tricks, but had a so-so showing.
The next year, it was raining while we were building the car and the paint would not dry. So we put the car in the oven to dry the paint. It was too much and split the wood. We finished the car anyway and it took first place!
It just means all the tricks help, but luck is needed too. We saw alot of professional looking, parent built cars, but you never know when a car is just "right". Kind of like musclecars.