I believe it will get too hot. It will fluctuate from 145-165. The best way to do a cold smoke in a vertical is to buy a pellet tube. Leave the unit off, light the tube, let it burn 5-8 minutes then blow it out like a candle and it will start to smoke. Put it in the smoker and close the door and you will have your cold smoke.
Pellet Tube at Amazon
That's what I had in mind. Let it set in smoke mode for a couple hours then crank up to around 225 to finish. Still new to pellet smoking (bought this for my lazy smoke days). Trying to get it least half of the smoke flavor like my charcoal / wood smoker produce.On the smoke setting your meat will never get done but I have done thick bone-in pork chops for 6 hours on the smoke setting just to try it out and had some pretty good smoke flavor. Then cranked it up to finish them off.