I dont have an electric any more so I am not smoking my fish on a pellet grill (eddies to be exact)
but when I used a coockshack smo20 I took a 1 inch dowel and put it in the door so I had a gap and then took a bungee and tied the door shut.
I was able to hold temps more in the 150-160 range this way.
There is an issue with this, as the extra air causes the wood to burn up much quicker. It took me a while to figure out how to manage that.
I simply added smaller chunks of wood on a more frequent basis.
There is one additional issue and thats the wood is often harder to get to ignite. Every now and again I would have to fire up the smoker (as in turn it off and back on) so I coudl get the next chunk to light.
Sounds like a lot of work, but it really isnt for the couple hours it takes to smoke the fish.
Since my pellet grill wont go that low, i simply do it on 180 and dont worry about the protien any more....but thought I would share another way if you are interested.