I’m no expert, but sometimes the pipe is just slid into the clay thimble, and packed around with rope gasket.
A round insulated liner in an oval or rectangular clay liner is a non-issue, and in fact standard.
Beautiful house! What’s with the shielding behind the stove, are you not meeting prescribed clearances?
Thanks ashful! We love this place. We moved in 6 months ago. The old stove was a a home made stove designed by the previous owner. It would burn hot really well but not economical in terms of wood consumption and not efficient at all. Hence the large slate 'heat shields' Not needed anymore but we like like the artistic/rustic quality they add.
I'm thinking of a 5.5" liner kit with insulation on top of that. Does that sound correct? I was thinking if I do 6" liner, it will be right up against the clay liner and probably damage or make it impossible to drop the liner in. I'm looking at this setup from Rockford: https://www.rockfordchimneysupply.com/round-flexible-custom-kits.php