By pulling the 4 rear skid mount bolts, and lifting slightly on the rear bumper, you are actually raising the drivers farther away from the ground. The track goes over the top of the drivers and back to the ground, so by lifting the drivers, you are actually changing the attack angle. Even though you are only lifting the drivers just a little bit, it still makes the attack angle on the track even steeper than it was in the stock position.
The attack angle might not mean to much on the trail in, but once you hit the steep and deep, the shallower the angle, the better the ride. JMO.