Lots of discussion on using the AMNPS in the Smokin-It # 3 (SI3), or any of the SI smokers for that matter due to how tight they are. So far I have not had any issues doing a cold smoke with the AMNPS or a hot smoke with an empty smoker during test runs, until last night.
I put on a 9lb butt at 11:30 last night, used a mixture of Cherry and Bourbon barrel pellets nuked for 1 minute prior to loading. I put the AMNPS towards the front of the smoker where the drain hole is, on the right side of the chip box, being sure to poke the foil at the drain hole. I placed the butt on the left side of smoker to prevent it from dripping onto the pellets. All was well and off to bed I went.
Here is the setup, AMNPS and butt placement
At 6:30 this morning, this is what I saw
Looking at the burn, I'm guessing I got somewhere around 3 to 3.5 hours of smoke in the 7 hour period it was unattended. The pellets rounded the corner and fizzled out. I think it was further from the element and drain hole where it breathes from, causing it to go out. I did not have this problem with an empty smoker, so there must be just enough humidity from the steam coming off the butt to make the environment unsurvivable for the pellets as they burn into the 2nd row. You can also see here where I folded the foil up on the right side of the chip tray to act as a gutter to direct the juices away from the AMNPS. That worked well, when I looked over the pellets there was no drippings on the unburned pellets. I added 2 chunks of hickory when I saw this to the chip box for the remainder of the cook.
So now I need to decide weather I should drill a hole or 2 in the bottom of the SI3 or just hot smoke with chunks moving forward. I'll need to do some research on that, if you have done the drilling mods on a Smokin-It please chime in.