Yeah, I did a bunch of research and pulled a lot of ideas from all of the things you guys had posted over the years. I was considering putting a cover, at least partially, over the lower port like you had done, to increase pressure on the top port. But so far, I haven't needed it. Honestly, reducing the amount of free air available to the lower port with the seals probably was enough to keep sufficient power diverted to the top port. And it doubled as a way to keep the airflow directed.
I will say it probably helps that I have less than 10' of flex hose in the total system, so I'm not getting much loss there. And the collection bag is made of felt and probably doesn't filter much. But, I have it placed just outside the garage when in use, so it can blow all of the fine dust it wants into the outside air. So it passes a lot of air.