Oh - and in a simple analysis like the one above, which neglects rolling resistance and the rider's own propulsion and what have you, the slope doesn't matter. It will affect the absolute terminal velocities, but not their ratio.

Talking of propulsion, if we figure that strength is proportional to weight and that the rider is pedaling all out, then the heavier rider gets a bit faster again. But you can't say how much so until you get down to real numbers for slope, surface area, and rider power output.