Wow I can actually post my first post.
I too have an Elmira Oval (this is the first Finley cookstove reproduction from the early 80's and then the heartland company began making them under their name as the model 1903).
I have been working along towards burning coal as this stove has the coal set up and the previous owner burned coal happily for many years.
the manual states 6" for this stove and nothing bigger for what I assume is the draw purposes.
I've only had this up and running for about a week now so I'm no expert by any means, but the manual is extremely vague and confusing. There are three bell baffles on this stove. One in the front on the ash door, and two on the left side. All are lower than the burning chamber.
Then you have the oven baffle which is a slide. So far it seems to like to be open to get direct flow through to the pipe and then as the stove gets going you close the vent to force the air to swirl around the oven compartment before it leaves the stove. I'm not sure if it's better to just leave this open unitl I want to cook but at the very least leave it open to get the fire going at first. It is supposed to create more resistance which in turn should mean more draw but that remains to be seen.
Additionally there is the coal burning kit vent which is the one draws air over the coal bed. I heard over the coal is better for burning and under/through is best for starting. It's all kind of confusing but hopefully some old cookstove vets out there can shed light on this as I'm as lost as the original poster!
More questions to follow and a big THANK YOU to everyone who adds input on this forum. It's the BEST RESOURCE for heating with coal on the net.