When you compensate, I think you should compensate from what the spot meter tells you your settings should be. I think the matrix metering is actually smart enough that it tries to compensate on its own. So if you try to compensate from the matrix metering, you might actually overexpose by too much.
You might want to take some using the matrix metering to see how they turn out. Maybe the camera is so smart that it will get white as white. I think I read somewhere that the matrix metering can do that.