I had a contractor install a true north tn20 stove into a masonry fireplace inset hearth with chase - all new stove pipe single and double wall. Where the double wall connects to the single wall and goes into chase there is this questionable connection where a crimped end of the single wall pipe is attached to the double wall adapter that goes thru masonry vertically into chase.. This guy keeps telling me it's the right way. I have not seen any other installs with exposed crimp ends used. I want to know is it just a cosmetic issue or is it a safety issue as well or am I the problem? I can get more photos if necessary.