Need answer real soon

That's not too hot, but don't expect much worth eating from a 4# flat.

Usually I'd say cook the pork over the brisket because the drippings will help the brisket, but you might want to keep such a small flat away from the heat, so maybe the top shelf would be better.

In any case good luck. Next time go for a real brisket. Packer, 12# or better with a good fat cap. Much more forgiving.

I agree with what Todd G. said Appleass. I'd want the pork fat dripping on the brisket, and I'd want a larger brisket. But I believe it'll work out well for you anyway.

I'd start it out under the pork, and keep an eye on it. If it starts to heat too much, switch your shelves around.

What are you smoking in?