I have an Englander 30 with a 30' chimney and a SS flex liner inside my old chimney. I always thought the secondary flames were exiting way to fast, and the doghouse air sounds like a jet engine. So I did an experiment. I have a T in the chimney pipe with a cap on the end. I cracked the cap open a little at a time. And now the stove runs way longer, with great secondaries. I have a baro damper ordered.