i have recently built a new house and put in an Opel 2. I have just started burning and have mixed results. I am burning hickory that I got from a local handle factory. The wood is all kiln dried chunks about the size of a hammer handle. I am trying to be cautious about over loading the firebox. The fireplace works great but I can only get about 2hrs of burn time in about 8 hammer handle size chunks. They are about 16" long and 2" square. I am pretty well sure I could add more but I really don't want to overfire. There are no temp gauges in the fireplace for me to look at so I am just staring at the flue pipe on top of the fireplace and looking for it to glow (which it hasn't). Am I being too cautious? I have read about people loading these full to the top with seasoned wood, but I really don't want a runaway. Any advice? Thanks