I am planning to upgrade the memory of new macbook pro. The current memory specs of my MB is ddr3 1067mhz at 1gb each Bank. The supplier told me that I could also use 2gb ddr3 1066Mhz on one bank side by side with 1 gb ddr3 1067Mhz on the other bank. Is this permissible? He also told me that there is no available dd3 1067Mhz memory module in the market today.