I'd like to finish my chimney with my clay flue and cap/spark arrester, and get started using the oven. I'm not ready to put the roof on, but when I do it's gonna have a double wall steel pipe going through it. So it seems logical that I should be able to build up the brick around my flue and then attach an anchor plate (at the top) for the transition to the pipe, which will then go through the roof.

Does anyone see a problem with this?