- jhsdigital, I believe its not so much the heat from the fire box as it is the airflow coming into contact with the reverse flow plate the way it does that causes the hot spot. Any time the airflow has to take a turn, it will heat that area the same way a river will eat away the bank .
What you want to do is get the air flowing horizontal BEFORE it comes in contact with the reverse flow plate, adding the deflector plate will do that, and the deflector plate will absorb the heat rather than the reverse flow plate.
SQWIB'S is one way to do that, and there are several other ways. But as long as the air is going horizontal before it contacts the plate is all that matters.