Some other views of the alignment used in the hinge mounts.
In-place back drilling is difficult with clamps in the way, and limited space for tools. Drill and bolt first then move clamps and try an angle drill for a better reach.
Note the large portions of the F-668 bulkhead snipped away - removing a section of the web which was alread drilled, dimpled, and riveted with the F-871 fwd top skin. There will actually be another 'layer' added to the hinge mount - an F-644 R&L brace. The F-644 attached to the F-671 fwd top skin, and the hinge mount. This makes it difficult to position/align. One web site accomplished this by removing the entire subpanel assembly, clecoeing it all together with the top skin, and inverting it on a bench to work from the bottom side. It's a thought ... maybe.
