The last three figures of my serial number is 9VV. I bought the base model of Mac Mini with 2x2GB ram. I plan to upgrade and replace one of the 2GB with a 8GB ram. I read in one of the support answers that "RAM should be installed in pairs or the machine will suffer true performance set backs." Does this mean they should be of the same capacity as well? Will it affect the performance if I use a 8GB ram in one slot and a 2GB ram in the other?