Duct heat from Englander 30NC upstairs

Move cold towards hot - one must have conviction to get convection. Slow and steady with a dash of patience wins this battle.

Check you local building codes. What you do depends on a) local codes and b) type of ceiling in the basement.

In our Ontario codes, with a non permanent ceiling (i.e. not drywall, unfinished) you can cut registers between floors, but there is a setback from the stove (iirc it's 6ft). The idea is a small (4X10) duct hole near the stove (but respect the setback distance) and a second hole at the other side of the room to allow cold air to fall back down to the basement. A small register fan can help move the air up a little.

If the ceiling is finished, then typically a full metal duct is required between the ceiling and the above floor. In some locales, a fusible damper is also required to shut the duct to prevent smoke movement either upstairs or into the ceiling cavity. Something like this or whatever your code needs https://www.acklandsgrainger.com/AG...balProductDetailDisplay.do?item_code=GFN2TGE1

We have a dropped ceiling in our basement, so what I did was to remove the tiles and insulation and cut a 4X10 near the stove, then removed the hvac connection from another across the room to create the circulation effect. I also used a small register fan on lowest speed. Net effect was a gradual warming upstairs. Not huge, but a few degrees most of the time. We ended up putting an insert in the LR so don't use the downstairs stove much any more, but when we did, this way it heated the whole house.

Again, I repeat, check your local building codes, that is actually find them and read them carefully. In most cases anyone in a stove shop or internet forum has never read their local building code, but will offer "factual" responses. It's painful to read (all legalese stuff), but read it and enlighten yourself.

oh yeah, and insulate that basement asap.

To get heat up, you also need to get cold down. You really need have a second duct farther away from the first to allow cold air to drop back down to the basement. In our codes any opening must be at least 6 ft away from the stove.

Look at a Tjernlund Airshare floor to floor model. It will be a lot less hassle than building the plenum and in the end less expensive, I think. I did what you are proposing years ago on my Dad's place. We put a large (as in you could walk around the boiler) sheet metal box over the stove/boiler and ran a 24x24 duct up to a heavy duty floor register in the hall way. This was actually off a boiler which I had built for him. That was piped into the baseboard heat. It was uncomfortably hot, but Mom and Dad just opened the window and smiled. Pleasant memories!

Your proposed 6" duct is to small to really move any air. It would be a max, if everything is right of 125 cfm.