The 3rd contractor told me that he has a friend with a cat stove with a 15' chimney run was getting creosote dripping down the chimney due to not enough draft.
What's involve with getting an extension? Thank you.
For example (broken link removed to http://www.rockfordchimneysupply.com/rockford.php?item=FlueExtender)
Dripping creosote from a 15' flue is more likely from wet wood or improper operation of the stove, or both.