I planned to use duravent double wall pipe from the top of my new lopi endevour wood stove, to my new stainless chimney liner. I bought the duravent appliance adapter and tried to slide it into the stove collar. It fit nicely but inside the collar there is a metal 90 degree angle piece welded to the inside of the collar that stops the adapter from sliding in all the way on one side. Am I missing something?