So the top baffle which is currently under the lower driver would now be on the opposite/back side in relation to the lower driver?
If you are looking at the first page of cabinet plans (via the web site), then instead of the drivers mounting on the left side of the box (side profile), they are mounted on the right side of the box.
Brace A (at the top of the box) moves to the other side as well.
You also move the tube connectors to the opposite side of the box too.