Wondering if you know the grade of the 16 lb brisket your butcher cut up? Choice or prime? It looks like a very, very fatty prime. Your pics show a very small point (on the top in one pic, and then on the bottom, and a very heavily marbled flat. Terrible waste of that cut of brisket to cut it up. The only variable with the whole brisket would be cook time, and I don't think "practice" on a cut piece of whole brisket tells you much about how to cook a cryovac flat or whole brisket. You will probably get a good result with low and slow cooking, but the exposed thick fat layer will render out early in the cooking, so be prepared for lots of fat in the drip pan. Let us know what happens, and good luck!