New Banco box project

Hy everyone!!!  from Madrid Spain I'm New here
I am building a batch box and I want to ask you if it's posible to put double size of bricks (2 tiles) for the chimenie instead of 1 tiles of bricks, without   the 1thbarrell around the bricks. Only put the outside big barrell
Thanks

Ola Manuel.

The less mass in the heat riser, the better. But if you use insulating firebricks,  you can do pretty much what you want. For a batch box, a barrel is not optimal, check your clearances.