What that looks like to me is a triangle shape that you put over the vertical dividers. Is that right?
BTW -- Several weeks ago, I was smoking something and my MES quit (don't remember if it was when the controller died or a heat coil connection). I moved the food (think it was salmon) to my Weber Propane unit. Turned the propane burners to low, 225F or so. I put the AMNS that I was using into the Weber, but made the mistake of putting it down on the "flavor bars" where it was perhaps only a few inches above the heat sorce. I had it in the center, with the center burner turned off.
When I was done, I discovered that it had warped slightly. It is still a good rectangle with straight sides, but does not sit level. Don't think that has any impact on its ability to do the job -- but It should be a warning to others that reinforces the "keep it away from the heat source". I can only imagine what might have happened if I had used my usual 500F grilling steak temperature.