I'm moving my Heat N Glo fireplace from an elevated platform back down to the floor and redoing the fireplace surround, mantel, etc. I did the original installation approximately 12 years ago and used Direct Vent exhaust piping by Simpson Dura Vent. What I discovered is that my existing pipe is 8 3/4" in diameter and the internal pipe is 5" in diameter. The new Dura Vent Pro is 8" and 5" and will not match up with my existing pipe. I need to know if I need to rip everything out and start over with the new pipe or if there is an adapter or some other way to work with my existing pipe. Thanks, Jack