Today I prepared the tunnel cover support ribs. I drilled screw holes in both the ribs and bulkhead to final size #19, and checked the fit of the parts. Having already drilled the bulkhead screw hole to final size in assembly with the F-704M angle stiffeners, I didn't have a good way to align the smaller cover ribs on the bulkhead, so I drilled these to size separately (photo1). The pre-punched alignment was perfect (photo 2).
I then drilled the holes for the various sizes of snap bushing in the cover support ribs. To lessen the chance of misdrilling these, I marked the hole sizes right on the parts (photo3). I then deburred all the holes and edges prepratory to priming.
Drilled the small ribs separately.
Screw holes align perfectly through all three pieces.