Reccommended Flue sizes direct from Italy

[sonomacast]

I found this on an italian Oven building web site
Diametro del forno diametro minimo canna fumaria in cm
da 60 a 80 ----cm 20
da 80 a 120--- cm 25
da 120 cm in--- su 30

Costruzione e uso del forno a legna

Translated... Translation result for http://www.fuocoelegna.it/costruzione.php

[stoveup]

My Italian is nonexistent and the translation is, um....interesting. However, it looks like the chart is recommending a 10" diameter flue (approximately 25 cm) for a 42" diameter oven (approximately 100 cm).

I believe this is somewhat larger than the FB plans calls for.