Yes! We need some pics! I loved doing stuff like that back in the day.
I never got to build a C02 car, but we did have a lab in AP Physics (senior year HS) where we had to build a box no bigger than 10cm^3 that would protect a pringle from a 10# weight slid down a track into it. I built the biggest box, and built a smaller box inside to hold the pringle. The smaller box was suspended by an elastic band from each corner and held at off-angles from the faces. It took 5 hits on the same side and the pringle didn't break.
Edit: BTW- It was normal corrugated cardboard.
OK! You can have the thread back now!