Just want to update everyone on the changes I made and how things worked out. I was having problems last year. Smoke spewing out on reloads, couldn't start a fire unless 45F or less, setting the smoke detector off, difficult start ups, long warm up times, bad burn times. I purchased a new section of round flex to replace the ovalized through the damper and cut the damper opening to fit it. Increased my chimney height 4' with an Extend-a-flue and the pipe inside the extend-a-flue insulated. I removed the original leaky blockoff with one I made using directions on this site and caulked it. Stuffed each seam with furnace cement, replaced the original home-made 30 with a true 30, removed a mis-matched connector, put 6" slag insulation above the block-off, enclosed the chimney penetration in the attic, lastly I'm now burning 21" split lengths instead of 16". My house improvements this year was adding R30 to the attic, replacing a leaky window in the basement , and insulating one wall of my foundation with R10 XPS that was a walk-out. Results are better than I'd thought. No smoke into the living area, cleaner glass, start-ups are a piece of cake now. The attic insulation reduced my heating by 13%, insulating the walk-out wall of the basement I'm pretty sure it reduced my heating 20%+. The other things, like fixing the chimney penetration in the attic I'm experiencing the mass of the fireplace inside the building envelope now especially the room behind it which is a bathroom, nice the bathroom is the warmest room in the house in the morning. I suspect I've cut my wood use 30-50%. When we light a fire the house increases temperature 8-12F on the lowest setting lowest amount of wood we can burn efficiently. Getting close to oversized unit at this point!