I would title this thread as more about fit then geometry. Seat set back is a big factor relating to how the torso deals with your upper bodies weight. It also affects how the bike is balanced/steered. I see a lot of riders with what I feel are seats too far forward, their pedals are more under them. A common complaint is hand or shoulder/neck discomfort. It sounds counter productive to slide the seat back to lessen the weight on one's hands but what happens is that your torso muscles can better hold the body up. Think about this. when you lean forward where does you butt go? It needs to move rearward or else you fall on your face. Andy