Really cool! I modified a clamshell style oven last year, and it's been working great, but this design is bit nicer because you dont have to open the top, which lets out a lot of heat.
Where did you source the heating Element? I took mine out of a second oven, but even together they're only about 1200W.
I also wonder if you'd get better leoparding if you tried adding some convection during the cook, like a low speed fan pointed in.