So it appears the tap isn't really going on much. and after reading the AD I wasn't actually doing it properly myself.
(should be on both sides of the base at the D-spar / Skin Seam)
AOTW: It's like looking for a secret passage in an old library. You tap along the blade looking for
ting - ting - ting
if you get a
ting - ting - thung
close the doors and put you hand in your pocket for a blade.
Has anyone found a potential delamination yet?