You can use them, but heavier steel is preferred. I made mine out of 12 guage but mine was really just a test to see how cheap of a smoker I could make. Whole rig cost less than 50 bucks. There are a few ways around it though. If you make a reverse flow like I did, I added 1/4 inch plate on the bottom for the floor/drip tray. The heavy plate helps in absorbing heat and releasing it slowly. On windy days, the wind will strip the heat from a thin walled smoker, thats why I have to do mine in our barn when the winds howling. You also going to go thru a bit more fuel trying to maintain the steady upper temps and the heat will disipate more than thicker walled units. If you were to use them, I would run them like HELL FIRE GRILL did below, a vertivle smoker. That way the heat has no choice but to go by the meat, I think that would work better that a horizontal design unless of course you added some heavier steel inside the cabinet. I think if I had to redo mine, knowing what I know now, I would have made it into a verticle smoker like HELL FIRES.