So in the process of installing new (well i bought it a long time ago) woodstove (Drolet Eldorado). I'm getting there, but while messing around with the ceiling support i was trying to get this chimney adapter into a 12-18 double wall adjustable stove pipe (the top part of it) and it just doesn't want to slide down very far. Of course i could grab the rubber mallet and pound but not sure if that is the correct method here. I'm using all supervent stuff. Thanks for the help.