No, it doesn't mean cut the cooking time in half. It will, however, cook slightly faster than the full 3 pound version. At the temperature your recipe recommends, just check it after an hour or hour and a half to see how its coming along. IMO, 325 is about 120 degrees too high for a braise. I'd be looking at something around 200 - 210 for a good braise. Braising is a technique usually applied to tough cuts of meat that are meant to cook low and slow so that the connective tissue gelatinizes rendering the meat fork tender.