Properly fitting a closure place in old fireplace

[grahamA]

I've opened up the old fire place in a pre 1900 property and planning to install a multifuel burner (already purchased) and have put a new 6" liner down. I'm in the position where i think I need to fit a closure plate in but i'm scratching my head as to how to fix / cut the plate so that it fits snug in such an uneven chimney (None of the walls are striaght or even). Also there is an old hood still insitu which i was thinking to leave as it reduces the opening but not sure how to fix the closure plate to it. I was planning on fixing the closure plate at the top of the hood and try to seal the bottom as best i can, is that a good idea?

 

Would a cement board be easier than a steel plate? 

 

 

[saveasteading]

2 minutes ago, grahamA said:

Would a cement board be easier than a steel plate? 

Yes. You get lots of shots at shaping it to suit.

[grahamA]

Any tips on how best to shape it?