i should also add that if you do my little experiment, you will also discover that your hip angle changes as you slide forward and back on the chair seat. as you move forward, the hip angle opens. this forward position facilitates a lower front end for a more aero position. when you move back, and close the hip angle, you have to be careful not to pinch your pedaling stroke. if your knees are whacking your chest when in the drops, then you've either gone back too far, or you have to raise your bars a bit.