I have a Bubba Keg. For a long time I was able to cook my ribs at 225. This last time I was not able to go below 300. Nothing has changed except the size of the lumps. I'm at the bottom of the bag and the lumps are all small. My question is....how much does the size matter? The lower vent is closed to about 1/8 inch. Any smaller and the fire goes out.