I just tried PC_FN_LEVEL2 after you refer me to the wiki
I am customizing the keyboards for symbols frequently used in vi editor. Page up/down maybe useful but is not a neccessity. Currently I am very happy with my mapping and I am shy that I owned N900 for a year but until recently a member here tell me the keyboard mapping features! Now I seldom use the on-screen virtual keys toolbar unless I need to copy and paste text.