Thank you, The ceiling box is just sitting in the ceiling opening. Im going to have to attach everything from the roof side. I wasnt able to push it into the ceiling as far as I want (3" down from the ceiling) which has me thinking that the box is hitting the roof decking. I wont know for sure until I get the roof opening cut and have a look inside. If the box sticks out past the shingles I think I'm supposed to bend the edges of the box over the rooftop and nail down. If it doesn't go that far and I have room to install the insulation collar, Ill slip it on. Ill send pics.I think that is the attic insulation shield. If so, it goes on the attic side of the support box if the top of the support box ends before the roof. The purpose is to stop blown-in insulation or any other debris from falling into the support box which must remain clean inside. We haven't seen pictures of the chimney part of the install yet so I am not sure if it's necessary for your install.
Thanks again for all your help~