Take a look at my oven and this flu liner

[vincentvintris]

Good day,
This is my oven with the dome pretty much closed.
I could only find this 4x8" clay flu liner. (see lying in the oven entrance)
I'm still wondering if this would be big enough.
I'll built the second arch and set the flue liner notched into the arches.
That way I'll have a vent opening of 4x20" quickly reduced to 4x8".

Does that provide enough draw?
I might be able to use two of these flu liners side by side.
Any suggestions would be great.

Thanks
VV

PS. One pic shows a simple handmade tool that worked great to clean mortar out between bricks, when I left gaps to cut bricks for later. (I built the structure without form and it worked well for me to install standard size bricks first, leave gaps and then cut bricks to size for those gaps.)