Yeah, the tiles above didn't really do much. Also, note that the top rack of tile is about one third the width of the rack below (just one row of four instead of three rows of four.) It didn't even seem to have much of an effect on the part of the pizza that was directly below the tile.
I made two pizzas and the first one was on the verge of being burnt in large parts while the top still looked very blonde. There was no color or blistering on the top parts of the edge crust. That was added with the broiler. I did my best to get the pizza in as quickly as possible to avoid heat escaping, but it didn't seem to make a difference.
One thing to try is to simply cook at a lower temperature, maybe more like the 450F or so, and then both parts should probably cook evenly. But, of course, that will be a slightly different style of pizza. I suspect that would work well for a Chicago tavern style.
Another crazy thought I had was maybe to remove the top grate, get a few fire bricks to put along the two sides of the quarry tile, and then have some kind of mesh or grate above to get another full layer of quarry tile something like three or four inches above the pizza, and see if that will radiate enough heat downward. I'll need to cut down the tile properly (as you can see, the tile very slightly hangs over the edge of the grill as it is, but it
just fits when the cover is closed, but four inches up, it definitely will have to be cut to fit.)