So the outlet of my stove is 7.5 inches. A 7 inch pipe is to small and 8 inch is to big. Am I missing something here?it has and 8" flue insed of the collar. This is my first wood stove and I'm new to all of this. Sorry for my ignorance. Lol. I'm worried that if I buy the 7" single wall pipe to connect to the stove it will be to small and not seal. What are my options?