I recently completed my mail box mod on the masterbuilt. .. My problem was that I couldn't keep the A-Maz-N pellets to stay smoking. I followed the directions with the pellets.
Fill tray to the top but not overflowing
Light with propane torch for 45 seconds
let the flame burn for 10 minutes
blow out and let it smoke
Only problem I had was keeping them smoldering. I tried full flow through my vent hole, cutting it to half and 1/4 flow. The best it got was about 3 hours of smoke and burning up one side of the tray and quitting at full vent. I have a 2" vent hole covered by a magnet on the front door of the mailbox.
SO.. any ideas? It was getting a good draw, because when they were actually producing smoke it was working great even at 1/2 & 1/4 venting. Maybe some holes underneath the tray to vent right up into the coals?