Continued riveting upper and lower fuselage channels to firewall brackets. Countersunk holes in each upper fuselage channels for three nutplates, one of which that will be under the F-1042 E gusset. Riveted nutplates in place, then riveted upper fuselage channel to gusset. Countersunk hole in F-1042 bulkhead and riveted gusset to bulkhead.