PWF setups are the first setup I saw 6/0 caster settings....very close to Volkers 6/-2(out of this world) setting. Negitive caster would rip the front end of your car to bits and pieces.

You might try going the other way with your caster, say 2/4.The more split in the caster, the more the car will want to cut into turns. Needless to say this setting may not work if your setup is built around a "reverse" caster setting.