I knew I would open up a can of worms here.
Sweep. First the air doesn't move behind the plenum and actually I've looked at the deflectors and they are really an after thought on this stove. They run across the top of the stove as does all of the air from the blower. They don't even flow air over the whole top of the stop, only about half of it at best. Really just have of the front half or so. I think the whole blower system was an after thought. If you look at it. It doesn't move air from around much of the stove. The deflectors don't deflect across much of the stove. Anybody that has a Summit insert can tell you that even with the fan on high, air only comes out the left side of the top vent. If you look at the deflectors, the air isn't even moving across the whole right side, Just the back right. It's a case of we have a great stove and we want to turn it into an insert and that calls for a fan, so lets stick something on it.
I have a sheet metal brake and I can make more and better deflectors. I can even experiment with them to see what's the best.
I doubt doubling the airflow would cool it off past secondary ignition, The secondary ignition occurs below the insulated baffell inside the stove. The blower air goes across the stove above it and above the exhaust to the chimney. but that's not really what I'm trying to do. I'm more concerned with moving the same amount of air, but doing it quieter. Running the fan at half throttle is pretty quiet, wide open its very nosiy, it keeps me awake at night. Running two at half throttle will be much quieter than one wide open.
Your right I'm starting year two on the insert. I didn't want to change anything the first year. I wanted to get the hang of things and establish a baseline.
I'm going to insulate above, behind, and beside, the insert with rockwool. This will keep alot more heat in the stove and alot less going out the chimney and behind the stove. I want as mush as possible coming into the room.
I have an OAK on it now.
I also understand that it is possible to move air across a surface so fast that little heat exchange occurs. The 160 CFM fan doesn't max this out. I check with a thermometer last year. Half fan and full fan produce about the same temperature of air, just less volume.
That said. Two fans will let me sleep at night without the noise, and with better heat deflectors and airflow, and insulation to keep the heat in the stove instead of up the chimney, I think I can get more into the house.
Anway, I hope somebody can answer the original question. I'm planning to do this mod either way.
Thanks again.
Oh, and when it's done I'll be sure to post pics on Elks forum to get him started.