Gang, I'm remodeling the rec room in the spring, and want to move my p61a to a different location in the room. House is built on grade, and there are two places I'd like to put it, both of which require going through a cinder block wall. After drilling the required size hole with a rotary hammer, what kind of pipe? Can I get away with standard pellet pipe, should flexible stainless be used, ??????? Any advice would be appreciated, thanks.