Robie Hobie wrote:
One has to stretch less and thus retains more "pulling" power to return car. Two is simpler, but a much longer stretch and the possibility of the car not returning as the cord ages and stretches.
I think you have that backwards. If only using one bungee cord tied between the two cars, then that bungee has to stretch more because it has to account for the full travel of both cars. In other words, if the traveler tracks are 18” long, then with two bungees, each cord would only need to stretch 18”. But with one bungee, when both cars are traveled all the way out, that cord would need to stretch 36”. Plus, with one bungee, there is less total cord in the system, so it will wear out more quickly and provide less consistent tension in the system through the range of traveler car positions.
sm