Continued to fit the firewall. Began by marking a center line on the bottom aluminum angle of the firewall. Installed the bottom forward skin, and lined up the center line with second row of rivet line. Drilled a couple of holes to keep everything lined up. Measured clamped, measured again... Drilled the skin to the firewall flange... Clamped, measured again... to make sure everything was holding true. Drilled the logerons to the WD-602 steel firewall brackets.