Not really - it depends if the brisket is the same thickness. Cooking time depends not on the weight of the meat as much as the thickness. When you're looking at different briskets at the store, you'll notice that the thickness will be the same but some pieces are just longer than others. The cook time in the pressure cooker should be the same for them. I used 75 minutes for my 3.5 and 4.8 lb. pieces because they were about the same thickness.