Newbie RMH questions

Hi I have a new small (1.5 story 20'X24 with finished walk out basement -- where stove will be) and well insulated (R-30 walls R40 ceilings) passive (with some active ) solar home in Eastern Ontario. It gets cold here , last year we had 6 weeks of -20C but if its sunny heat of the sun will heat the house up to 60 F without any wood being burnt. Of course it does nt shine everyday and never at night! I currently heat it with an old airtight stove that I am very unsatisfied with. I have downloaded and read Ianto Evan and Leslie Jackson's book a couple of times. I still have some questions I like to post to the group.

My biggest concern is system size. From what I have read in the book I should be looking at an 8 inch system to reliably keep the house warm but my chimney flue is 7 inches. Does that mean I cant have an 8 inch system? My understanding of the book is that an 8 inch system with a 7 inch chimey flue will cause smoke to back up. Is that right? Am I limited to a 7 inch system? I have never heard of one. Would a 7 inch system be enought to keep my house warm if 6 inch is nt? Dont know if it matters but my chimney goes up through the middle of the house has a span of at least 40 feet and rises about 3 feet above the ridgeline of house. The draft on it is fantastic. If I have to put in an new chimney to accommodate an RMH of adequate size then I wont be putting in a RMH.

I am still at the design stage . Trying to decide between a heated bench, a heated bed and a just a big thermal battery.
I have some questions about each.

HEATED BENCH:
What have people's experience been with dogs and cob? If I build a heater cob bench I dont have to tell you where my dog will be while i am at work in the dead of winter. Dogs tend to scratch their beds as they get ready to sleep. I dont believe cob would stand up to that kind of treatment. So I am thinking of putting a veneer of brick on the bench. Can I use cob as 'mortar' for the bricks?

How do people use their heated benches? For short term warming up after comming in from the cold or do you sit on in while watching TV?


HEATED BED:
In a word FIRE! As much as I would love a warm bed to crawl into everynight I am scared of setting my house on fire if heat from last nights fire hits my matress while I am at work. Is there a way to design a safe system? If not its a no go for me.


BIG THERMAL BATTERY:

My here idea is to get two discarded heating oil tanks I think they are about 350 gallon capacity and use them as two bells. I would encase them in a cinder brick cube. I would fill void space in cinder bricks with gravel and between tanks and cinder bricks with urbancrete , rocks and gravel and then for aesthetics cover the whole thing in tiles.

I think the big thermal battery with two bells is my choice. But I'd love other people's thoughts.



Kind Regards

Jeff

Will you live in the walk out bassement?

If not, forget setting the stove there. They need tending.

Batch rockets need less tending, but they still do.

Good point. It will be living room/den. It is dry and in the winter the warmest part of the house and in the summer the coolest so its the most comfortable place to be.