Nate, the trailing arm calculation is just to illustrate how much angle change the spring lift/axle drop causes based on the length of the articulating member. The correction must come from somewhere else, or you have to reverse the lift. There are a couple of obvious choices for the correction method, one easy, one hard. The hard one is to cut off all the axle mounting hardware (panhard rod, trailing arms, spring perches) and reweld them at the new location with the angle corrected. THe easier one is to notch one of the two trailing arm bolt mounting holes and rotate the axle to correct the angle. the drawback of this second method is twofold. One, the spring is slightly canted on the perch, and second, the panhard rod is in a slight bind on it's pivot.