I was in the same situation and used the DSE bolt-on perches during assembly. Once I was able to set the car at ride height I got under and set the angle, bolting down the perches. Then I removed the rear and welded the bottom half of the perches on. You don't really have to do that 2nd part, especially if you hope to tune the suspension with the pinion.
I forgot the number, now, but I went pretty negative to reduce the shock the Z-rated tires would see. Sounds good in theory, right?