For our mousetrap car we decided to go for a 4 wheel design, because we thought it would be more efficient and stable. At first we used the skewers for our axles with the red and white straws. We switched to the thick axles/dowels after our skewers broke.
One of the main issues we had was with our wheel alignment. We found that our car would drift a bit to the left. we resolved this problem by adding two extra layers of cardboard on the wheels, and also the thicker axles helps by making the wheels more sturdy. In the end we made it 17m down the hall which puts our team in 2nd place. All of our group members participated in helping to build and design our mousetrap car.