Similar question. I have 2 6x6 posts, centered under new deck stairs with Four 2x12 Stringers. I was thinking of notching the 2 center stringers in order to hang/install a 4x6 beam between those posts using Simpson hangers. So the notched stringers would rest squarely on the new beam. Doing this to add more support cuz I have the 4x6 scrap left over, might as well put it to work! Thanks.