I should have specified that they are steel fire box with cast iron jackets; F45, F50, F55. It's been hard for me to find a backup stove, secondary burn, that has a steel box and rear-vents. The Jotul model that vents low enough for my lintel height is too much stove for my space. Not strictly secondary, but the same thing with the Woodstock steels; The IS would fit under my lintel but the AS is a better fit as far as output.
So is that the only way it would be legit with air-cooled chimney in a chase, if you ran an insulated liner inside of that? What else would work in a chase..standard Class A double-wall chimney, as would be used above a ceiling in a two-story house?
Does the insulation look like an R-13 batt you would find in a wall, or is it something stiffer? How did you end up putting in the baffle and insulation, insulation above the tubes and the stainless plate on top of the insulation, as it apeared in the diagram?
I don't guess you had time to get the cast collar attachment, so I'd be interested to see what was done with the stove's flue exit connection, and if it connects to an insulated liner inside the air-cooled chimney as bholler asked (I doubt it.) Pics would be great, if it's easy to get the top portion of the mesh surround off to get a camera in there. Seems like you may not be a big pic guy, though..
From your description, sounds like that 1.3 cu.ft. box may only heat the immediate area, living room and maybe master bedroom. But any amount of heat will beat propane only. You can play with ceiling fans or whatever you have at your disposal, to make use of the heat you
do get out of the stove. You certainly won't get meaningful heat all night with the small stove.
I'm looking forward to hearing how the little 18 burns (visible secondaries, air control, etc.) now that you've got it closer to how it should be set up. The suspense is almost unbearable! I love new-stove fun!