As I worked to fit the shim I realized the gap was tapered from top to bottom, i.e. the F-712 bulkhead and aft face of the WD-409 were not parallel. I could see the F-712 was tight against the WD-409 through the tooling hole near the bottom. To make the shim wider at the top I kept the double thickness and then cut one piece shorter. Through trial and error I got the two pieces to fit well, so the gap at the top (where the bolts will eventually go through) was filled completely with good edge distance all around for the bolt holes. I tapered the edges, scuffed and cleaned the parts, and then used JB Weld to glue the two pieces together.
While the JB Weld set up I continued to rivet the J-channels to the skins. Got the four J-channels completely riveted and then moved to riveting the F-779 and F-711 to the side skin.
I mixed another batch of JB Weld and put it on the front and back of the shim. Put the shim in place, then riveted the F-712 aft bulkead to the skins.
