[Gtkradiant] Custom Map File Format

[David Jackson]

What is the best way to have GTKRadiant output a custom map file format?

I am developing a non-commercial game, and would love to be able to use 
GTKRadiant to create the maps for it.  However, I am having trouble with 
parsing the map file.  A simpler format would be great (plain vertices 
describing polygons instead of planes describing a brush).

Any help in this direction would be greatly appreciated.

David Jackson