The black bits by the elevator tube exits are pieces of cf tube that will be exit guides for my rudder cables. Modelltech supplied a piece of semi-rigid fiberglass to line the tuned-pipe tunnel...I probably should have glued it in before I glassed the center section but I didn't, so I had to go over it again. I never would have had the kind of confidence my flying style is going to demand in this thing. They also supplied a similar piece to create the part of the tunnel in the fuse bottom forward of the wing. This was pretty straightforward.