Insert for wood stove chimney?

[Starchy]

I have an elderly friend who just bought a cottage with an old airtight wood stove. This stove has an 8" flue, with double wall black pipe to the 8" stainless Selkirk metalbestos chimney. I believe the chimney is about 25 years old, but looks to be clean and in good shape. The stove burns well as she has had several fires and it seems to work well. The problem is that the wood stove is not certified by either UL or CSA, and the insurance company has said that it must be replaced with a new, certified stove. No problem except that all new stoves seem to be 6" flue, and the existing chimney is 8". Can a liner be added to the chimney to make it 6" or must the chimney be replaced as well?
Thanks for any input.

[HayZee518]

just use an 8 to 6 inch reducer fitting. put a 6 inch manual damper in the6 inch line so you can regulate the draft.

[Starchy]

Thanks HayZee518 for your quick reply. When my house was built, 9 years ago, I asked the contractor to install a chimney for a wood stove that I did not have yet at the time. He installed a 7" metalbestos chimney, and every stove I looked at to buy was 6". The store where I bought it said that it would be OK as the maximum limit for creating a good draft is 1" over the stove flue size. I have had some trouble over the years with back draft and have found that if the fire is really going, I am OK, but it struggles to burn when I reduce the air intake to the stove for slowing down the burn, after all it is an "air tight" stove that should burn slowly, I thought. My fear with following your suggestion would be that with a 2" difference between the stove flue, and the chimney, they might have similar or worse draft difficulties. AM I right here? I am no expert in wood stoves or chimneys.
Thanks again.