A double rack means twice the pizza! I have experimented with the "Roswell Rig" from Innovations by Chance, and here is the best way to align it for the Pizza-Porta. The rack is a great invention and holds 2 pizza stones. It is a bit narrow, but will handle a 12" peel. When you set the double rig in the Egg on the high portion of the fire ring (not in the plate setter notches) the top stone is a little bit too high in the Egg for the Pizza-Porta door. I set the rig down in the notches for the plate setter. (the plate setter then sits on the higher setting). I then space up the bottom pizza stone in the Roswell rig about 1/2 inch so that it is closer to the height of the BGE felt. I had an old broken Pampered Chef pizza stone and used three pieces under the bottom pizza stone. I also position one leg of the plate setter in the front to block the heat that can only escape from the vents and door.
This arrangement works very well. The bottom pizza gets good heat radiation from the top stone, and the top pizza gets all the dome heat reflecting down on it. Having the plate setter up a little closer to the bottom stone also helps deflect heat around it. I prefer to put cool/raw pizzas on the bottom stone for the first part of cooking just to keep that stone's temperature down.
Pulling the top pizza out of the double rack with a nice crispy crust.
There is plenty of room for the top pizza in this configuration.
A double rack does allow you to crank more pizzas out in a short time. We did 32 pizzas for a dorm party with one full load of charcoal.
Write to me if you have used the Ceramic Grill Store's rig with the Pizza Porta. The Pizza-Porta does accommodate the rig, but I have not cooked with it.