Just bought a house that has an exterior cinder block chimney and with a clay thimble...not enough clearance around the clay thimble, so I'm replacing it. If I try to install any of the standard thimbles insul-flu, saf t, I will have to remove all combustibles and put a hole through the wall as my cinder block chimney is only 18" wide. My stove is 6"...if I use Class "A" chimney pipe through the wall and with 2" inch clearance, I will reach the cinder block chimney without putting a hole through my wall. My question is how do I connect the chimney pipe into my clay flue liner inside the cinder block chimney?