They used 1/8' plate to do mine and it works fine. They did a hell of a job I must say.
Check out my baffle. Im using a piece of the plate as a heat plate which is laying on top of SS threaded rod. You'll see the threaded rod in the above photo. Instead of bolts in the top holes, I used threaded rod with nuts on each side. Works great.
Just to keep experimenting, I want to get a piece of sheet metal and stamp louvers in it starting about 2" in from the firebox. Always thinking and experienting.
The white chit is crisco for the seasoning!