And as far as exactitude goes, it's important the riders be identical in physiology and metabolism, and that we're talking about watts measured at the bike, not total watts. Not just because a heavier rider has more resistance to overcome to move the bike, but he has to work harder just to move his own legs. And if one rider is able to sit still above the waist and the other has to dance all over the place, total watts would differ even at the same cadence and speed, but of course watts through the pedals would be the same. I think this is why fit is so important. It's not just about positional comfort, it's about efficiency in movement, too.