Vent opening up to Flue Adjustment

[tdibratt]

Hi, have a question about the vent opening up to the flue. I did an arched opening so I have a few full bricks and then the middle is half bricks which leaves me a about a 4.5 by 12 opening for the smoke to go up the chimney. But because of the arch, the opening flairs out towards the sides and then the smoke needs to constrict to go up the chimney because it is an 8 inche flue liner.

Is this working OK for people or should I add 2 tapered bricks, 1 on each side, to bring the opening back to vertical. I would add 1 half brick tapered on the left side and another on the right side.

Hope this makes sense.

Thx, Tony.