Decided to build the mailbox mod for my AMNPS. Previously I was putting the tray in the smoker, which seemed to work pretty good. I had the chip tray loader tube pulled out about an inch an the top vent opened all the way. Seemed to usually get a nice, thin blue smoke. Adding on the mailbox mod tonight (I didn't add any holes to the mail box), I lit up a "dry run" and the smoker is blowing white with a tinge of even brown smoke. Should I be closing the top vent up to choke the draw down? Try to seal the mailbox up more? Or do I have it all backwards and actually need to get more airflow by adding holes to the mailbox? I have 20 lbs of buckboard bacon to cold smoke this weekend and don't want to mess it up. Worst case is I will go with my previous setup this time, as it will only be in the 40's.