@fastcat: Some sort of architectural salvage place eh? IIRC there may even be some closer. Yes, an old cast-iron floor grate would be just the thing for that use.
@SteveZee: Thought about putting in a thimble but, that plan was nixed by the better half. Would put stove a little close (~6' or so) to the bottom of the stairs, if a kid fell or ran down stairs and didn't stop in time...
Again, thanks for all the input, now working on a safe way to get the stove downstairs. Very easy to move on the level, or on a slight slope, just a piece of plywood with rollers of pipe, but it'd be Interesting in a Hurry to try that on ramps on stairs
even without rollers I suspect it would slide a little too quickly.