I don't know if that's really necessary. Spend some time working the soft aluminum with some bending and flexing to make it conform to the body of the WSM better. You should be able to get it to seat against the middle section pretty well. Then, after you've cooked on the WSM five times or so you'll have built up enough natural gunk that things should tighten up on their own.
Your main areas of focus should be the door and then truing up any out of round issues with the charcoal bowl or center section.
Good luck