Yes, 2sided mapping relates always to the whole model, not to the selected part. You need to use 6sided Mapping two times, one for the Upper' part of the hand, one for the 'inner' part of it.

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