With the help from advice on this forum I placed an order for the Mt Vernon Quadrafire Insert. The dealer stated that my present metal insert and piping would have to all come out. For venting up my wood chase he ordered 25' 3" Pellet Liner Flex Kit (Duravent). I had read on another posting here that flex can not be used with a wood chase. Is my dealer steering me wrong or is this actually a safe and correct option for the Mt Vernon? Thanks for any opinions. Happy 4th!