My friend weighs 100 pounds more than I do and I own his ass on climbs, we're pretty even on the flats, but on down hills I have to pedal like a gerbil on crack just to hold his back wheel.

On my own I have noticed that my bikes that are heavier descend faster when they are coasting... when I was a kid we used to make pinewood cars and after making them as aero as possible the best way to make them go faster was to add weight that exceeded the enforced limits.

I do not ride in a vacuum... the spacesuit kills my aerodynamics.