I still haven’t received an email back from Van’s about the top rib, so I gave them a call. They’re going to take a closer look at my pictures and get back to me, but they did say that the top rib often requires a bit of massaging by the builder to get everything to line up. Since I may end up using this rib anyway, I spent some time tonight getting it bent such that all of the holes lined up and the skin laid flat against its flanges. Here is the rudder fully assembled to see how things lined up.