The bones in your butt are your sit bones. That is what is SUPPOSED to support you, not the tender parts. Your bones will get used to it after a while. Your legs should not be extended all the way, that is what might be making you hurt. You should have a slight bend in your legs when the pedal is at six o'clock and the ball of your foot is on the pedal. I believe that if you look down at your foot your knee should just about cover the view of your toe.