The 2 sites I have used in my very limited sous vide cook...Neither has a chart for pounds, or mass. ChefSteps says Steak, Roast & tough cuts (Here’s where sous vide shines brightest—you’ll be blown away the first time you slowly cook a cheaper cut like brisket or chuck, converting it into something with great flavor and texture.) The other ChefMate as I look over it has no advice for cooking a Brisket!
ChefSteps says Medium is 149° for 12-48 hours, with 24 being the sweet spot, but absolutely no help with mass or weight of item being cooked. So I guess I will go 48 and see where we are, can always bag it back up and cook!