I see what you're saying.. that brings up another point.. right now my oil furnace is running up a 9x13 clay flu.. I was considering running a 6 inch stainless liner for the wood stove and a 5 inch stainless for the furnace.. it's a straight shot for the oil furnace only 4 feet to the chimney.. the manual says not todo this.. I figured if they had indepenant flu what could it harm.. especially since its going to be rare they run simultaneously... any thoughts? I'm going to make a new thread soon. This is my last question here.