Dave, I assume you're using the Keystoker powervent, right? I'm running something very similar.
I'm not running up the wall quite as far as you, but basically it's the same setup and it works fabulously. I had to go through 10" of poured concrete with a 5" core bit to get outside, and I'm using Simpson Pellet Vent Pro 4". It's all sealed and/or self sealing, so it's just a matter of locking it together and lighting the fire. It's $$$, but high grade stuff. I didn't want to have to worry about ugly silicone, etc. trying to seal regular vent pipe and I also didn't want to have to worry about clearances. I've yet to get the exterior of the pipe above 100F.