Thanks for the detailed response.
The points you make have made me consider variables that I might not otherwise have figured into my newbs calculations
Perhaps I am trying to run before I can walk, but I do like to experiment. I will initially be making something that 'must' function via the info here (I think I will buy the Wood Burning Stoves 2.0 DVD set about RMH so I can see what is happening with different processes.)
Looks like I will have to go for 6-8" - where I am siting this, the free space is relatively minimal, I will need to excavate the floor or suspend the pipe work. This is going to be a small annex build with the possibility of running pipes into the rest of the building -if- I can get it to work properly.
The former seems preferable as then I have the floor mass for heat retention.
The 2nd install would be for a workshop - greater area & would be better as a radiant only build as far as I understand it, not being ocuppied 24/7. 50/50 radiant/storage might be a better way to start thinking about it though. (I.e. a limited amount of mass+a lot of radiant metal surface.)
I all cases I think the gasifier angle with firebrick/fire cement components is where I'm heading.
One thing - I was thinking of using oil filled containers as mass to store heat rather than burning it. I kinda wrote off burning even waste oil given Big Oils relentless destruction of the planet.
Is a clean oil burn even possible?
............Better head over to DuckDuckGo.
Thanks again for the detailed specifics - it's a great help!