Chimney gather in open fireplace / BBQ

[Gerhardt]

I am in the process of building an open fireplace / BBQ in the outdoor kitchen area. The intention is to put in a chimney gather like the one in the attached photo. 

 

I have a couple of questions which I hope someone can help with.

 

Should the smoke gather sit on the lintel or should I put it up higher in the chimney breast?

 

Regarding the lintel, should I use a 200 mm wide or 100 mm wide lintel at the top of of the opening, this is not a structural engineering question but what I want to know is if I use a 200 mm lintel with the smoke gather in the attached picture connected to a flue, will smoke spill over or will the the smoke to be sucked up the gather into the flue. My preference is to do a 200mm lintel but I can do a 100 as well if needed.

 

 

 

Edited September 6 by Gerhardt