What are the measurements on the rear sway bars you are using? You can calculate the wheel rate of your rear sway bar and up your front roll rate by a proportionate amount through larger TB's or a larger front sway bar to get to neutral.

To answer your original question, rule of thumb is to lower front tire pressure or raise rear tire pressure to decrease oversteer. Never used it to tune overseer/ understeer myself; and obviously you can go too far. Try 32 front 38 rear. (I don't think just tire pressures will get you where you want to go, though)