Finished match-drilling the center section, and drilled the F-623 baggage compartment side ribs. Here it is, flipped and positioned so I could finish the -623s.

The -623s have to be fluted before being match-drilled to the center section belly skin, so that means finding a way to mark rivet hole locations on the rib flanges. I was able to get close enough by holding the rib up to the F-770 side skins and marking the approximate location of each hole. Easy enough. Then the ribs were clamped into place per instructions and drilled.

The last step in fitting the F-623s was fabricating small shear ties, or clips, that provide a load path to the F-705 bulkhead in the front, and to the F-706 bulkhead in the rear. The front clip is pretty straightforward…

…but the aft one has to fit in a pretty narrow space between the F-623’s rear flanges. If you follow the plans, the clip really doesn’t have sufficient edge distance so I followed Brad Oliver’s lead and altered the design a bit to provide some extra “meat” around the hole.

Here are the clips after fitting…