Hello, I am considering the purchase of an indoor add on wood furnace. I am interested in hooking it up to the existing ductwork as it would be costly to install a complete separate system just for the add on furnace. So here is where I need some advice, All of my existing supply duct is under my home in the crawlspace. I have only found add on wood furnaces to have the duct coming directly from the top of the units. Would it be a bad idea to 180 the duct off of the top of the add on to penetrate the floor and tie into existing duct?