I would like to move the chimney closer than the 4 1/2” spec'd in your directions. Is there a minimum distance back from the front of the oven the I can place the chimney?

Mattone Barile & Mattone Barile Grande Ovens
1

4.5" is about as far back as you can go – after that, it pretty much so skips the chimney and just exits out the front of the oven.