I've been heating about 2600 square feet with my old late-80's Sierra. Up to now, I have not paid much attention to flue temperature, firebox temp, or anything like that. When I get the fire quite hot, hot enough to heat the room it's in above 90, the firebox starts roaring like a jet engine. I mean that I can hear air being forcibly sucked in the intakes and see a rolling flame of what I assume is combustion gases at the top of the firebox. I have decided to not open the door when this is going on- no need to add fuel, obviously. The Mrs. is scared that this is "overfiring." Yes/no/maybe so?