Hello, I have a macbook pro 13 2012 with 4gb of ram. I want to upgrade to 16 someday but i want to see if i need less first. Is it possible to buy just one 8gb stick and use it with the 4gb stick of ram to give me 12 gb ram? Someone told me this is a bad idea because of the channels...but I didn't understand him. is this true? Or will it really be the same as 12gb?