A Deflector Baffle and Tuning Plates or Convection Plate are the 2 best mods besides New Thermos in lower corners of the doors. They don't need to be sealed up all that much- just need good airflow or draft thru the smoker. and a grate 2-3-4" off bottom of FB so ash can fall and fire get good airflow.
I went up to Oklahoma for a few days a cpl weeks ago and borrowed an UnModded OK Joe- didn't even have a baffle. I went to dollar Tree and bought 2-$1 cookie sheets and put them under cooking grate side by side on Firebox end with a tinfoil water pan on top and I had only 20-30* difference end to end.
You can see them in this pic