[mypalmike]

I think there is something particularly special about rubber in the design. He stretches it extremely tight. Even with the leverage of a crank, he strains to compress it to the length required, and the rubber holds up. It might be possible to achieve the same result with older materials, but the design would likely be much less compact.

[CrankyCanuck]

No, I don't think so. His design respects the inherent latency to accelerate a looooog set of elastics. Instead of stretching a set of elastics over a long distance, he uses a heavy bundle and stretches them over a short distance. It still takes a lot of effort to get that stretch, but all that energy is released extremely fast..as the elastics don't have to travel very far to do so.