You need some caster just to make the steering "stable" i.e. the caster preloads all of the steering connections and gear and caster makes the steering want to go to straight forward so if you run lots of it the car really wants to go straight but will also add a "cross jacking" affect if you turn the wheels alot. Cross jacking can also be increased by using a spindle with lost of king pin inclination, which is why spring cars run 10+ deg. king pin inclination and 7-10 degress of caster. When they back it into a turn and then "steer right to go left" the right front wheel picks up the front end and also this causes the left rear to carry more weight which is just what a sprinter wants. BUT sprint cars have fairly rigid frames so this jacking cause by lots of caster and king pin angle actually does something. Most of the cars at B'ville are long, narrow and or have fairly flexable frames so the cross jacking affect of the added caster is not as prominate. Give her 10 degress and if she don't go straight give her some more!
Rex