I am installing a Woodstock Progress Hybrid Stove and an exterior double walled insulated stainless steel chimney system. I have no other choice on the chimney, it must be an exterior setup. The stove pipe will go right out the back of the stove, through the exterior wall, and straight up 21 feet. I am a little concerned about having a stong draft with an exterior chimney. Has anyone else gone this route? And if so, what were your results? Thanks in advance for your input.