I purchased a new pellet stove and am supposed to take delivery later this summer. I ordered the "standard install kit" which I'm told comes with 25 feet of chimney liner/exhaust vent piping. I measured from the floor of my fireplace to the top of my chimney to make sure this was enough liner. That measurement is about 23 feet. Do I have any reason to worry that 25 feet is not enough liner? I guess I'm not sure if any waste needs to be calculated into the mix. Thanks.