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I have a cast iron skillet in the bottom of my SH38 where the chip tray used to be.
I put a couple of wood chunks in the skillet and put the tube up on the chunks to raise it off the bottom of the skillet a little so it gets better airflow, while the skillet still catches the ash.
Though the AMNTS was designed mainly for propane smokers during hot smoking, you need to be careful using one when cold smoking for if you fill the tube up with pellets, it will generate way too much smoke. Not the TBS as desired. When I use my AMNTS for cold smoking, I will fill the tube up maybe 1/3rd full, then when laying it down horizontally, shake it sideways. It ends up with a small layer of pellets along the bottom. Otherwise, I use one of my AMNPS trays.
The cast iron skillet is a trick I did a couple years ago for my gasser. It helps spread the heat from the burner more equally around the smoker as well as improving better air flow.
The skillet I used was a 12 inch, it sits on a grate with 1 inch legs that was left over from the side burner of an old grill.
Before that I had placed a piece of steel angle on either side of the burner hole to set the skillet on. The chip tray supports were not strong enough for the weight of the skillet.
What Cmayna says makes sense, my first smoked cheese came out pretty strong using a full tube, though it is mellowing a little after a month.