Huh, seems like if you have low rear grip it would oversteer unless the front have even less grip. In that case I would think you need different tires, or just have to take the corner slower if grip is that low.

My under steer was caused by the rears pushing too hard and the fronts couldn't compensate. Going from 10k to 5k in the front let the outside front wheel spin faster and helped the front get a little more pull around the turn.

Reducing toe-in (running 3-3 block) reduces the truck's willingness to want to drive in a straight line since each wheel isn't trying to push to the middle as hard. Easy way to image this would be a 90deg toe in obviously the truck would not move forward or side ways no matter what you did to the front.

I can see why having less rear toe can make it difficult to handle on rough track since the bumps make the truck want to turn and there is less stabilizing force in place, but I don't understand why it makes the rear end stiffer?