If you are trying to build a "silk purse out of a sows ear" of course weight doesn't matter. But, a portly car will never out accelerate, brake, or corner faster than a lighter one. It's like pulling a trailer behind a car when you add 1500 pounds for all the convenient gizmo's. I weigh 175 at 6'2, and a lighter driver would be faster. You really notice the weight difference in a kart, motorcycle, bicycle, walking/running, or even a horse. I don't know how I could possibly carry around even an extra 100 pounds every day. I know I could accelerate, turn, or stop faster, plus it would hurt more to fall down.