I just get a Masterbuilt 40" 4 Rack Electric Smoker w/Cover, Window, Remote yesterday 6-6-14 my first smoke about 3 hours into it I notice the gap. It take 10 hours at a temperature of 230 degrees to smoke spare rib and one baby back and it still was not done. No smoke ring. But my question is what can I do to close that gap so I will not lose no heat?