Didn't want to let too much more time go by before thanking you for creating the LBE. I'm loving using it and learning from you and others on this thread. How're your latest air scoop tweaks working?
Following the trail you blazed, I cut out a side vent, albeit mine's rectangluar and a bit larger than your original. I use firebrick splits on top of the cooking grate and a Pfalzgraf 14" x 1/2" round stone on top of that. I used the small Weber coal grate inside the lid (thanks Retrodog!) in my LBE, supporting two foil wrapped half firebricks. That leaves about 2" cooking clearance.
I got an old stone oven 16" stone, but with its feet and total 3/4" height I don't have enough clearance under the top stone grate, so for the time being I'll stick with a 13" max pie size. I'm not sure, but I think the open gaps at rear and sides of the firebricks help with heat flow - but makes for hotspots and uneven baking unless turned frequently.
I've set the LBE on top of a spool table topped with floor tiles, the works with bottle roll on a convertible hand truck (for easier transport from garage to patio and back.) Pictured below.
Like others, I found the 18" cooking grates sagged (pictured) - especially with the weight of the firebrick splits - though I'm not sure it'd ever fail altogether. I really like the looks of the metal plates Essen1 and others have made, but I don't weld and custom work is pricey here so I got a heavy duty charcoal grate instead - unfortunately about an inch smaller than the Weber cooking grate, but with the support tangs pulled out and bent upward, it stays in place (shimmed with balls of foil)
17" DIA. (ROUND) NICKEL PLATED BRIQUET GRATE Code:BG9 $14.14 at http://www.allpartsgrills.com/item28619.ctlg
I think I'll try Retrodog's baffle ring, but leave the front cut low so I can spin the pie with a spatula without lifting the lid.
I'm also keen to try your whole wheat crust - your pies are beautiful!