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No, it doesn't. That time guideline is for full packers where the thickness of the packer changes as the weight is higher or lower. A 5 lb brisket flat will take just as long to cook as a 9lb brisket flat that is the same thickness. Wish I had some helpful time guideline to give you other than to say that it will be done when it's done (do the poke/probe test to know when that is.)