Hello like the title says my quad 3100 millenium doesnt burn for more than 2 hrs at most. If i try filling the box up to near full the fire just takes off even with both dampers closed with stove tops reaching 700-800. I only have 10.5 ft of flu from top of stove, I was thinking i might need a taller flu but wouldnt that just increase airflow and not help so much controlling it? I know the numbers companies advertise arent always legit but 2hrs seems pretty low compared to the advertised 10-12. I burn fir wood averaging 12-17% moisture content. Any idea's? Thanks!