Opinion for rocket stove

Ho permies, i'm fabio from italy and i'm gonna build my 4 rocket mass...

my question, please, is: I can build my rocket starting from a larger section inside the combustion chamber, the smoke channel and the smoke tower ... and gradually go and hold onto the chimney that is small, after 5 mt of smoke channels??  that is, start with a section of 330 square cm and get to 170 square cm

Thanks a log
Fabio