That's the exact idea I had in mind, with the slots...
I made one, but made it about 1/8" shy from all edges. This gives plenty of room for air and I didnt want to make 3 of them tonight.
I am going to try it out tomorrow, as i dont want to test right before bed. And because of the Mild weather, I will be using the Quad tonight. But its done and ready for tomorrow when I get home from work
I finally cleaned the exchange tubes. I haven't had the top baffle plates off, in almost 2 months, or maybe longer. Over a 1/2" of ash on them

Definitely gonna be warmer tonight

My ash is almost level with the pot, ash pan is about 8" over full... Its a Quad. They just burn.... and burn....... and burn....
Nothing burns like a Quad