Pinion Angle Help

I am using RMs boxes. I plan to use the upper rear hole so the front eye will be raised up 1.5" to lower ride height.

I am ordering a new Dana 60 from Dr. Diff. He wants to know what spring seat angle I want. I could go stock and rely on shims to fine tune or I could take some out. I.e. 5 degrees is stock, 3 degrees would be the new settting etc.