Sorry, about the question aout the second uv coordinates.
What I still don't know is this

#2 How can we set the uv vertices to a different skin than the first one?

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