One lesson I learned a while back is that Glass and Graphite don't mix. They bend differently. In short both being tubular - when bent form an oval. One material forms a smaller oval then the other causing one tube to crush the other. Then you're back to repairing again.

The most difficult task you face is in locating a piece of graphite that can match both top and bottom. Ask you're friends - if they are like mine they have a few broken rods laying around.

Try contacting the manufacturer - sometimes they can be helpful as well.

Good Luck!