Nice looking shoulder there, congrats!
Fwiw - I have a new Oklahoma Joe's Longhorn, and did my second smoke yesterday. It only came with 1 temp gauge on the side nearest the smoke stack.
When I was shopping in grocery store, I picked up a couple of oven thermometers, that hang or stand, and set one on each end of the cooking grate, near where the meat ended on each side.
The right side was hotter than the left, by about a 30- 40 degree difference.
I also found the temp on the left hand side of the cooking grate, to be about 50-75 degrees cooler, than what the thermometer read on the top of the smoker, that came with it. However it was raining hard, I was under a pop up canopy, and the high only got to like 68 degrees.
I have ordered a custom convection plate for the OKJ, and custom charcoal basket as well, from Horizon. I am hoping the plate will help even up the temps across the smoker.
Enjoy that shoulder, it is looking delicious!