Can both of the SODIMM slots in the 15" and 17" PowerBooks be used for memory upgrades? I.e. If I buy a stock configuration with 512MB of RAM in one slot, can I pull it out and put 2 1GB sticks in there for a total of 2GB? The reason I ask, is because aparently the base memory in the 12" PB is soldered directly onto the motherboard. I assume this is NOT the case for the 15" and 17" models, i.e. the base RAM can be removed.