Urbee and Edison2 both rely on reduced parts count for manufacturing efficiency. The Urbee seems to have lost 100lb, between the Wired article and the Gas2 one that references it (1200-->1100lb). The VLC, at 1400lb, carries 4 passengers and the windshield isn't horizontal.
RBFuller put 250,000 miles on a rear steering car. Of course, he wanted to lift the rear wheel off the ground aerodynamically and steer with the two front wheels, too.
