Out of the box, the kettle pizza leaves a lot to be desired. The issue I had was too much heat on the bottom, not enough over the top.
The prograte/tombstone is great - the cordeirite stone works well, and the openings in the prograte allow for placement of coal/wood. I did not get the baking steel top as I had some better ideas, so I had some 3/16" steel plates cnc plasma cut into 21.5" diameter circles.
I placed one plate on the weber kettle's grate tabs.
The kettle pizza insert goes in with the tombstone/prograte, the tombstone/prograte now sits about 1.5" over the bottom plate.
The second steel plate goes over the top, covered with a perlcrete insulating layer. (I used a steel plate w/ the KP insert to cast the perlcrete)
The coal and wood will rest on the bottom plate within the large gaps in the prograte. I used two of the gaps, one on the side, and one in the back.