Right. That whole trailing edge rib fitting works better when you finally realize the piece you thought was the original, wasn't either. It was simply a better-modified but not completely matching replacement version. And the original pair, when you find one, matches enough with the pictures to be for the other wing, which you haven't started assembling yet. The other half of the original pair? Long lost - may not have ever had in the first place.
Back to sanding and repairing, cutting and drilling. Priming and bolting to follow!