Per 5730-2 Rev D, a modified flap assembly can be used to roto-peen radii < .375 (Rev C), and > .093 (Rev D). Nothing is noted regarding the roto-peen technique specifics, i.e., RPM, mandrel angle, flap assembly size, masking, etc. After several communications with Boeing experts we are still struggling to achieve coverage in small radii. It seems that time is significant (and long) making masking essential.

Who holds the secrets of the technique specifics?
L. Zellman