I can't give you any specifics since i havne't touched GT1 in over a year, but generally, the taller you make your gears by sliding the slider to the left (especially your final drive and 4th gear and up) the higher your speed will be. So therefore, if you make your first 3 gears shorter (slider goes to the right) you'll have great down-low acceleration but you won't sacrifice your top-end. YOu probly already know all this...