 wjtracy Senior Member Joined: Sep 00, 0000 00,000 0,000 0 Location: Northern VA (NoVA) Vehicle: 0000 Prius As far as Toyota design rationale re: weight, it probably gets into EPA rules for weight class etc. Also you get more cargo space without spare, whereas as the Gen0's slim down rear end takes away the ample space that the Gen0 had in its bulbous back end. 