By the way, one of my favourite Pinewood Derbys was when a kid mostly built his own Derby car with "help" from his very-unskilled Mom. He was probably one of the smallest and nerdiest kids in our Weblos troop (but a very nice kid).
His car looked terrible with poor sanding and drippy paintwork. And because it had such poor balance and alignment, it went faster backwards than forwards. But it weighted the correct amount and followed all the building rules. Initially, I was very sad for this kid and his very poor-looking car.
Meanwhile, like all these event, there was many "perfect" cars obviously built 100% by the parents with no involvement of the kids. Several cars came in display boxes and the fathers were so protective that the kids were not allowed to touch them.
So what happened in the end?
You guessed it! The "crummy" car won overall! Personally, I was delighted. My son built his own car too and it didn't look much better.....he got third overall (probably because I told him, "Don't spare the graphite").