And, for the rider's position to be aerodynamic, the stem must be significantly lower. Because of this, a slightly undersize frame is often required. If it's not possible to move the bars low enough in relation to the seat, it will be difficult to set up a proper areo bar position. Aerodynamics is everything if you're attempting to maximize cycling speed. In multisport racing, which is predominantly flat steady speed time trialing, we don t do much sprinting or climbing.
Mechanical resistance is also remarkably insignificant in comparison to aerodynamic losses or gains.
Aerobar position is another subjective positioning consideration that's difficult to define. So, this would lead us to believe that the more stretched out we are on our aero bars the better. But, another consideration is our power output and stress to our lower back muscles. I find that a rider given a trial and error session with a variety of aero bar adjustments, can always find a good compromise between comfort and speed. An example of this is wind tunnel testing results, versus the consensus among aero bar users.