Drilled relief holes on rear channels # 1,2,3,5 & 6 (7V6-2SP) & heavy rear channel # 4 (7V6-1). Cut and bent channel flanges on outboard side of channels. (7V6-3). Laid out rivet pattern on rear channels & rear rib angles. Drilled & clecoed rear channels to web side of rear ribs only.
