incase your intrested, i also have a N900 and got hexen running fullscreen. I dont advise messing around but, if you go to /usr/bin/ edit the hexen2 file there and change the width to 800 and height to 480 and it will run in fullscreen. Even though its OS2008 must admit runs pretty well so far


EDIT: Also id go to the options then "Go To Console" and do like Bind n togglemenu then type quit and relaunch so once your in game you can just press N to open menu to save or quit rather that beating the hell out of your power button.