I have a Oklahoma Joe longhorn. Although I know the sweet spot in the pit i decided to just go ahead and try to get even temps. I was getting 50-75 degree difference between the chimney side and firebox side. Sometime next to the fire box I was reading temps of 400+ degrees.
I had some 12"x36"x 18 gauge sheets in my shop so here is what I did.
I have the 20" version I took 2 sheets and overlapped them and tack welded the seams on both sides. Added a 45 degree angle, and painted it with high temp paint. It fits like a glove and the length is about half my smoker. Not sure yet if I will have to shorten it and add tuning plates. My ET 732
is arriving today so we will see what difference it makes.