I didn't have a look at the examples of this article.
For your purpose its enough to write a 'my.min_z = -70;' or what count of quants fit with your models feet.

http://www.puppenheim.org/
http://www.wuerfels-welt.de
Old Game Tutorial: http://www.puppenheim.org/MITutorial.zip
Free Game Editor: http://puppenheim.org/AlienalsWeihnachtsmann.zip
http://www.puppenheim.org/blender_starting_main_settings.txt