When rendering the extruded font "8" from arial.ttf, the back surface has a glitch in the middle where the top and bottom half of the "8" meet. I believe this is because the back surface vertices are extruded "outwards" from the front surface, and messes up where the top and bottom halves intersect. Please see attached screen capture.
Cheers,
kamion@hotmail.com
Screen capture of FTGL SimpleDemo