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That article specifically says you may miss it if you are perpendicular.Looking at the anatomical pictures here:
http://www.asipp.org/reference3/Lau2004PainMed.pdf
I doubt it matters whether your angle is steep caudal or more perpendicular as long as the tip of the needle is in the groove. I'm burning at 90°C x 2 with a 90° rotation medial in between.
I'll try a few your way to see if there is a difference in sensory stimulation.