I have an Oklahoma Joes Longhorn...it leaks like a sive around the door (thats another post). I was interested in insulating it...but from the inside.
There are times when it just wont hold steady temps and is really frustrating. The leaks around the Pit Door are because the door is warped, it just dont fit tight. My idea for that is to weld 1" flat iron all around it and then use a gasket of some type to seal.
But can you safely place insulation on the inside of a smoker? reason I ask is because I dont want the expense and all the work it would take to do it on the outside...I'll sell mine and buy a new pit if it comes to that.