I have a much smaller brisket. How much should I adjust the cook time?

Hi Sauertea, I hope this worked out for you, since I'm guessing it was for dinner last night! Since it will depend especially on the thickness of the corned beef, not just the overall weight, it's hard to say, so better to start early and check for doneness with the fork cue, since it will hold well till it's time to finish dinner.

It depends on how much smaller it is. You are going to have to just keep an eye on it to determine when it is done.