Could be a few things:

- You are not using the right Z value
- You are rendering the letters in the wrong position (try (0,0) )
- You are not using the right scale of the letters
- You are rendering the triangles in the wrong order (unlikely though, since it works in perspective view).

WILL asked me to write a little article for PascalGamer that explains how to do both 2D and 3D rendering at the same time. I might do that in the future, if I find the time.