You're joking right? You want to soften the front Anti Roll Bars to reduce understeer.
Generally, from my experience with FM2 and Fm3, and according the help rollovers, stiffening the front springs diald out understeer, and stiffening the rear increse oversteer.
Front stiffer = less understeer
Rear stiffer - more over steer
As a general rule

Anywhooo...!