I went backup on the roof and rechecked my measurements. Inside diam. of clay liner is 6-3/4".
I found a liner company out of Michigan that sells square liners. They offer a 5.5" square outside diam. liner. This would fit and with there 1/2" insulation would give me 1/4" to play with.
I found a liner company out of Michigan that sells square liners. They offer a 5.5" square outside diam. liner. This would fit and with there 1/2" insulation would give me 1/4" to play with.