Thank you all for the replies. It's definitely out of round, so I was able to squeeze the sides a little and that seemed to help a little. I'll still have to add the washers to push the tabs in, but that should solve it. Couldn't be happier with the smoker. Thanks again.
This was my third cook on my 18" WSM, and right before I put the turkey on, I noticed the water bowl had a hard time sitting in the center section of the unit (it actually fell off the first time I put it in). I managed to get it situated, then as soon as I put the top grate on with the turkey...