I have just ordered 4 x 1gb sticks for my mac pro (shipping). I understand that there needs to be matching pairs to optimize the RAM. Do I: a) install a pair of 1gb sticks in each tray and split the 512 chips between the trays as well for a total of 5 GB. b) put 4 gb in one tray and put the factory gig in the other for a total of 5GB Or is there another option? Advice on this matter would be greatly appreciated.