Hey guys. I started this thread and I have found that 6 inch plates work the best. So I have my baffle then 3 plates with ZERO gap from the baffle and firebox side. The 4th plate I have a 1/8 inch gap then 5th plate has 1/4 gap and from the 5th plate to the stack I have nothing. No matter how hot I get my pit no matter where I place a probe I run within 5 degrees at any spot in the pit. Keep in mind this has a lot to do with all the other mods I have done to my trailmaster limited pit. The gaskets, toggle clamps, and rtv caulk around the firebox all help maintain the pit temp. If you just put the tuning plates in without the other mods you will be chasing your temps and having to retune all the time. I have no retuned once since my initial pit seasoning and tuning fire. Just my two cents. I have pics of all my mods posted here or an other threads I started. If anyone has any questions on my mods let me know.