I have a new 40" with the large waterpan and the vent on top left. What is an acceptable temp swing? I have set to 240 to get 225. It goes from a high of 228 to a low of 212. I am monitoring with and oven thermometer and a ET-732 Redi check. Should I go up to 245 to bring the low up some? I will also call Masterbuilt to see if I need a temp gauge change.