What the droop screws do is allow you to control chassis roll. The further you turn down the screw the less arm that is on the outside in a turn can extend keeping the chassis flatter. Roll can give you more traction up to the point that you exceede the traction limits of the tire, then you loose all traction.
Extreeme RC magazine unlike the other mags is full of suspension tuning articles and the like. Ill look in my issues and list the article by month, I know there is one on droop.