i guess in theory you could put in a larger chip, the problem is that the chip is not a standard ram chip, It is custom at least to some degree, a replacement would be very hard to find.
PB G4 15" 1.2ghz - Pismo G3 400 mhz - iBook G3 500 "Jukebox"
"SawSmurf" G4 500 - Quicksilver G4 Dual 1ghz modding...